Questions every good NET developer should be able to answer

Question

My company is about to hire  NET developers  We work on a variety of  NET platforms  ASP NET  Compact Framework  Windowsforms  Web Services  I d like to compile a list catalog of good questions  a kind of minimum standard to see if the applicants are experienced  So  my question is   What questions do you think should a good  NET programmer be able to respond   I d also see it as a checklist for myself  in order to see where my own deficits are  there are many          UPDATE  It want to make clear that we re not testing only for  NET knowledge  and that problem solving capabilities and general programming skills are even more important to us

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Martin Fowler prefers design skills over platform knowledge  On the other hand you can ask a question which will show knowledge of design patterns and  NET platform like this    Name design patterns and principles you know and how they are utilized in  NET Framework

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I m with the guys that are looking for problem-solving abilities rather than the sort of thing you can look up and memorise from  101 top  NET interview Qs and As    Just to cite myself as an example  I tend to  know  the things I need to use from day to day   I tend to forget  and later have to re-look up  things that I use rarely   If you wanted to trip me up in an interview  it would be very easy   Nevertheless  I have architected and coded much of the infrastructure for a system that uses identical Business Objects and Data layers for its WinForms and ASP NET incarnations  and our codebase is robust and reusable enough for us to be able to support and develop 20  differently configured versions of the web site  as well as an increasing number  currently 5  of the WinForms application         with a development team of two   I used to work on a team as a tech lead  and my job involved quite a lot of recruiting and interviewing   My most spectacular mistake was hiring a guy that knew more about the technology we were using than all the rest of us put together  including me  and I counted myself as an expert   He knew everything         except how to write code that either met the requirements  or could be understood by anyone except himself   When I eventually persuaded the PM not to renew his contract  every single thing he wrote had to be rewritten   Structure your interviews wisely

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Honestly    What is  NET    If they can give you a clear answer as to what  NET is and what it isn t  how it s used  what elements it s composed of  etc    If they can convince you they know what it is  then chances are they know it pretty well   The fact of the matter is  many people don t really know what  NET is   Even those who write programs for it

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None  really   There are probably very simple questions that the smartest people in the world do not know the answers to   Not because they are hard  but simply because they just haven t come across it   You should be looking at the whole package and the skill of the developer  not whether they can answer an arbitrary question   If the question is easy enough to be answered in a short sentence or two  it s easy enough to just tell someone who doesn t know   You should be looking for their understanding of concepts and reasoning capability  not their ability to answer questions  every  NET developer should be able to answer

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Know the difference between reference and value types   Know that events are stored as hard references  i e  remember to unregister events or the application will leak memory    Strings are immutable

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A few more   What are the limitations of garbage collection   Know about finalizers and IDisposable   Be aware of the thread pool and when to use it    If you re doing GUI applications - be aware that Windows GUI is single threaded    Use foreach  I see a lot of people doing MoveNext etc

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None  really   There are probably very simple questions that the smartest people in the world do not know the answers to   Not because they are hard  but simply because they just haven t come across it   You should be looking at the whole package and the skill of the developer  not whether they can answer an arbitrary question   If the question is easy enough to be answered in a short sentence or two  it s easy enough to just tell someone who doesn t know   You should be looking for their understanding of concepts and reasoning capability  not their ability to answer questions  every  NET developer should be able to answer

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I m a fan of the following in addition to some of the questions already mentioned    What s a delegate   What s the app domain  When would you use the lock keyword  Are the standard library generic collection classes thread safe  What s an extension method  What s the difference between XmlDocument and XmlReader   How do you read in configuration settings from the application config file

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I would always look for the soft skills myself - no pun intended  So good OO design  test driven development  a good multi  programming  lingual background and all round general smartness  and getting-things done-ness I guess     An intelligent developer should not have any trouble learning the individual technologies that you need them to know even if they have never looked at them before - so I wouldn t worry too much about specific questions around WCF compact framework and the like   I would have them write some code - best way to find out what they know and how they work  Anyone can memorise the answer to  What s the difference between a reference type and a value type

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Martin Fowler prefers design skills over platform knowledge  On the other hand you can ask a question which will show knowledge of design patterns and  NET platform like this    Name design patterns and principles you know and how they are utilized in  NET Framework

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Here are some I ve used to filter programmers applying for jobs as C  programmers   What s the difference between a reference type and a value type   Explain the IDisposable interface  which C  language construct requires it and how you would implement it   Which exception would you throw if a null is passed as an argument to a method which has a contract that doesn t allow nulls for that parameter

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I would always look for the soft skills myself - no pun intended  So good OO design  test driven development  a good multi  programming  lingual background and all round general smartness  and getting-things done-ness I guess     An intelligent developer should not have any trouble learning the individual technologies that you need them to know even if they have never looked at them before - so I wouldn t worry too much about specific questions around WCF compact framework and the like   I would have them write some code - best way to find out what they know and how they work  Anyone can memorise the answer to  What s the difference between a reference type and a value type

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None  really   There are probably very simple questions that the smartest people in the world do not know the answers to   Not because they are hard  but simply because they just haven t come across it   You should be looking at the whole package and the skill of the developer  not whether they can answer an arbitrary question   If the question is easy enough to be answered in a short sentence or two  it s easy enough to just tell someone who doesn t know   You should be looking for their understanding of concepts and reasoning capability  not their ability to answer questions  every  NET developer should be able to answer

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None  really   There are probably very simple questions that the smartest people in the world do not know the answers to   Not because they are hard  but simply because they just haven t come across it   You should be looking at the whole package and the skill of the developer  not whether they can answer an arbitrary question   If the question is easy enough to be answered in a short sentence or two  it s easy enough to just tell someone who doesn t know   You should be looking for their understanding of concepts and reasoning capability  not their ability to answer questions  every  NET developer should be able to answer

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Here are some I ve used to filter programmers applying for jobs as C  programmers   What s the difference between a reference type and a value type   Explain the IDisposable interface  which C  language construct requires it and how you would implement it   Which exception would you throw if a null is passed as an argument to a method which has a contract that doesn t allow nulls for that parameter

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I suggest enquiring about blogs that they read on a regular basis and personal programming projects that they  have worked on as this will show a willingness to learn and a passion for programming

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I d not ask those  know something from the textbook  questions  but rather ask some tinkering stuff like     What does the foreach loop do in plain C    Expecting him to write a iterator loop   What s a singleton  Let him her parse a String to Datetime  expecting him her to use TryParse instead of try catch  Implement the singleton  strategy and command patterns Let him her Refactor a piece of code for testing  Expecting him her to abstract the external services away from the Unit under Test and implement his own Test-double of the service  providing no mocking framework    These are not 100  sure  depending on the person I may ask them    let him her guard a method from null input  expecting him her to use multiple returns to reduce nesting  how does a object initializer work  Expecting him her to write the thread-safe assignment    Also I d ask him how he she learned his her stuff and what he she is reading  what blogs  books

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Honestly    What is  NET    If they can give you a clear answer as to what  NET is and what it isn t  how it s used  what elements it s composed of  etc    If they can convince you they know what it is  then chances are they know it pretty well   The fact of the matter is  many people don t really know what  NET is   Even those who write programs for it

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A few more   What are the limitations of garbage collection   Know about finalizers and IDisposable   Be aware of the thread pool and when to use it    If you re doing GUI applications - be aware that Windows GUI is single threaded    Use foreach  I see a lot of people doing MoveNext etc

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Basic questions include    Whats the difference between an abstract class and interface  When would you want to use them  What s the difference between a left join and an inner join  What s the difference between viewstate and sessionstate  What s the difference between overriding and overloading a method  Explain how both are done  What s the difference between protected and internal  What about  protected internal   How do short-circuited operators work  Explain what the StringBuilder class is and why you d want to use it  What s the difference between a static method and a non-static method  What does the  volatile  keyword in C  mean  Explain what happens when you pass a  ref  or  out  parameter into a method  What s the difference between those two keywords  What s a weakreference  When would you want to use one  What s the difference between a DataTable and a DataReader  What s the difference between a value-type and a reference type  What does the  readonly  keyword in C  mean    I think it usually helps to ask your applicants to complete a simple coding exercise such as    Write your own linked list class without using the built-in classes  Write your own hashtable class without using the built-in classes  Write a class that represents a binary tree  Write a method that traverses all nodes of the tree  Write a method to perform a binary search on an array without using built-in methods  Draw a database schema for a blog  Each user only has one blog  each blog has many categories  each category has many posts  and each post can belong to more than one category  Ask your applicant to write queries to pull specific information out    Next  look for specific technical know-how     Event handlers  Create a class with a custom event handler  create another class which hooks onto the custom event handler   XML  Load an XML document and select all of the nodes with properties x  y  and z   Functional programming  Create a function that accepts another function as a parameter  A Map or Fold function works really good for this   Reflection  Write a function which determines if a class has a particular attribute   Regex  Write a regular expression which removes all tags from a block of HTML    None of these are particularly difficult questions for a proficient C  programmer to answer  and they should give you a good idea of your applicants particular strengths  You may also want to work in a few questions code sample that make use of specific design patterns    Edit for clarification     Seems that a lot of people don t understand why I d ask these types of questions  Let me touch on a few peoples comments  I m not quoting directly  but paraphrasing instead      Q  When was the last time anyone used volatiles or weak references   A  When I give technical interviews  I look to see whether a person understands the high-level and low-level features of  NET  Volatiles and weak references are two low-level features provided by  NET -- even if these features aren t used often in practice  answers to these questions are extremely revealing    A good understanding of volatiles demonstrates that a person understands how compiler optimizations change the correctness of code  how threads keep local copies of shared state which may be out of sync at any given time  and is minimally aware of some of the complexities of multithreaded code  A good understanding of weak references demonstrates that a person knows about the intimate details of the garbage collector and how it decides when to free memory  Sure  you could ask candidates  how does a garbage collector work   but asking about weak references gets a much better  more thoughtful reply     NET is a fairly abstract language  but star developers almost always have a deep understanding of the CLR and the low-level details of  NET s runtime     Q  Why would anyone need to implement their own hashtable or linked list   A  I m not implying that the Dictionary class is inferior or that people should roll their own hashtable  This is a basic question which tests whether a person has a minimal understanding of datastructures  Thats what these questions test for  bare minimum understanding   You learn about these hashtables and linked lists on the first day of Data Structures 101  If someone can t write a hashtable or a linked list from scratch  then they have a huge gap in their technical knowledge     Q  Why are these questions so crud-oriented   A  Because the title of this thread is  questions every good  NET developer should know   Every  NET developer begins their career writing crud apps  and 90  of all application development people do for a living is concerned with line-of-business applications   I think questions testing a persons knowledge of line-of-business apps are appropriate in most cases  unless you re looking for developers in very specific niches  such as compiler development  game-engine development  theorem-proving  image processing  etc

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I suggest enquiring about blogs that they read on a regular basis and personal programming projects that they  have worked on as this will show a willingness to learn and a passion for programming

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I suggest enquiring about blogs that they read on a regular basis and personal programming projects that they  have worked on as this will show a willingness to learn and a passion for programming

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Know the difference between reference and value types   Know that events are stored as hard references  i e  remember to unregister events or the application will leak memory    Strings are immutable

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Who is Jon Skeet

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What is a thread    What is the GC

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This is a bit of a variable question  and not really one you should be able to answer completely now  but one you should be able to answer when appropriate    What does the  NET framework offer to get task X done    Or more specifically    Does the  NET framework include an object that does X    For example  I recently spent a few hours developing an object that is optimized to store an array of Booleans and operate on it  such as doing a collection-wise NOT  OR  XOR  AND  set all values  etc  It wasn t until after I finished writing all my unit tests and tweaking it for the best performance possible that I realized my  BoolArray  object already existed in the  NET framework under the name  BitArray    This can be a tough one to answer since many times the best answer on what object   helpers to use is the one you do not know or fully understand  How wonderful the  NET world would be if everyone actually knew about even the simple StringBuilder  a basic tool that can increase performance significant amounts

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What is a thread    What is the GC

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This might not be what you want to hear  but I would recommend not focusing on narrow technologies  but on general programming and problem solving skills  Solid developers can learn whatever you want them to do quickly    I  for instance  am not a Compact Framework guy  so I might fail your interview if you went that direction  But if I needed to use it I could do some research and jump right in   Joel s book  Smart and Gets Things Done  has great advice for hiring devs and there are large juicy sections about the kinds of questions to ask  I highly recommend it

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Here are some I ve used to filter programmers applying for jobs as C  programmers   What s the difference between a reference type and a value type   Explain the IDisposable interface  which C  language construct requires it and how you would implement it   Which exception would you throw if a null is passed as an argument to a method which has a contract that doesn t allow nulls for that parameter

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I m a fan of the following in addition to some of the questions already mentioned    What s a delegate   What s the app domain  When would you use the lock keyword  Are the standard library generic collection classes thread safe  What s an extension method  What s the difference between XmlDocument and XmlReader   How do you read in configuration settings from the application config file

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I found these lists on Scott Hanselman s blog    What Great  NET Developers Ought To Know  More  NET Interview Questions  ASP NET Interview Questions   Here are what I think are the most important questions from these posts divided into categories  I edited and re-arranged them  Fortunately for most of these questions there is already a good answer on Stack Overflow  Just follow the links  I will update them all ASAP    Platform independent  NET questions   What is the difference between a thread and a process  What is the difference between an EXE and a DLL   What is strong-typing versus weak-typing  What is the difference between a Equals b  and a    b  What is boxing  Is string a value type or a reference type   What is the Global Assembly Cache  GAC   What problem does it solve  What is an Interface and how is it different from a Class  What is Reflection  Conceptually  what is the difference between early-binding and late-binding  When would using Assembly LoadFrom or Assembly LoadFile be appropriate  What is an Asssembly Qualified Name  Is it a filename  How is it different  How is a strongly-named assembly different from one that isn   t strongly-named  What does this do  sn -t foo dll  How does the generational garbage collector in the  NET CLR manage object lifetime  What is non-deterministic finalization  What is the difference between Finalize   and Dispose     external article  What is the difference between in-proc and out-of-proc  What technology enables out-of-proc communication in  NET   What is FullTrust  Do GAC   ed assemblies have FullTrust  What is the difference between Debug Write and Trace Write  When should each be used  What is the difference between a Debug and Release build  Is there a significant speed difference  Why or why not  What is the difference between  catch  Exception e   throw e   and catch  Exception e   throw     What is the difference between typeof foo  and myFoo GetType     What is the purpose of XML Namespaces  What is the difference between an XML  Fragment  and an XML  Document    XML Basics  How would you validate XML using  NET     ASP NET   What is a PostBack  What is ViewState  How is it encoded  Is it encrypted  Who uses ViewState  Why is it either useful or evil   What Session State providers are available in ASP NET  What are the pros and cons of each  What is the OO relationship between an ASPX page and its CS VB code behind file  How would one implement ASP NET HTML output caching  caching outgoing versions of pages generated via all values of q  except where q 5  as in http   localhost page aspx q 5   What are HttpHandlers  What are HttpModules  What is needed to configure a new extension for use in ASP NET  For example  what if I wanted my system to serve ASPX files with a   jsp extension  How do cookies work  What is an example of Cookie abuse  What kind of data is passed via HTTP Headers  How does IIS communicate at runtime with ASP NET   Where is ASP NET at runtime in the different versions of IIS  5 to 7

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Who is Jon Skeet

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Good questions I have been asked are    What do you think is good about  NET  What do you think is bad about  NET    It would be interesting to see what a candidate would come up with and you ll certainly learn quite a bit about how he she uses the framework

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I think it shouldn t be just questions  I know a few guys who are brilliant when you interview them but once they get to the real thing they are too much perfectionist I would say that they fail to code the task miserably    I ve been once interviewed and I kinda liked the approach where first employer gave me a technical questionnaire to fill in 30 minutes  If one is successful then he ll be called for a 1 hour interview covering Personality Judgement and Character finding questions plus technical jargons   Then I ve been asked to develop a three page web application in 6 hours time  The constraints impose in application was smartly covering major aspect of application development like a small ERD  Layerd Design  UI Consistency  controls specific problems like using Radio buttons in GridView and Fetching and displaying image types from DB on a web page  one algorithm development  security  Encryption  Hashing  Data representation and manipulation    Then Next day they followed by a 30 minutes discussion on the developed application covering performance bottleneck areas and improvements on design and used algorithms  And 1 hour optional test to improve your algorithm developed in previous step with a specific condition   So it took a fair amount of time but this way you can make sure that the person you are hiring knows at-least those concepts which are essential for a good developer to be

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This is interesting  and at the risk of getting this down-voted for putting in my opinion  as I am born deaf  being asked a question like that would require more effort in communicating my thoughts on my part personally    To be blunt  I really would not read too much of the typical questions  as the underlying paradigm is  How well can you vocalize your thoughts and understanding    that is really what the interviewer is looking for  Communicating is always my biggest weakness due to the way I am and can get frustrated quite easily   It would be ideal to have the knowledge and be the know-it-all type but unfortunately  there are some things I don t know  but not to be afraid if you actually don t know the answer and admit it rather than bluff through it  If an interviewer asked me a question like one of the above  that I would not be sure of or mis-understand mis-interpret the question  I would say it upfront  which can personally be embarrassing  but have learnt to handle that   You would be surprised at how many would actually waffle on and bluff through it in which at the end of the day get caught out with their  pants down  metaphorically speaking   My 2cents  Best regards  Tom

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This might not be what you want to hear  but I would recommend not focusing on narrow technologies  but on general programming and problem solving skills  Solid developers can learn whatever you want them to do quickly    I  for instance  am not a Compact Framework guy  so I might fail your interview if you went that direction  But if I needed to use it I could do some research and jump right in   Joel s book  Smart and Gets Things Done  has great advice for hiring devs and there are large juicy sections about the kinds of questions to ask  I highly recommend it

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I would always look for the soft skills myself - no pun intended  So good OO design  test driven development  a good multi  programming  lingual background and all round general smartness  and getting-things done-ness I guess     An intelligent developer should not have any trouble learning the individual technologies that you need them to know even if they have never looked at them before - so I wouldn t worry too much about specific questions around WCF compact framework and the like   I would have them write some code - best way to find out what they know and how they work  Anyone can memorise the answer to  What s the difference between a reference type and a value type

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Basic questions include    Whats the difference between an abstract class and interface  When would you want to use them  What s the difference between a left join and an inner join  What s the difference between viewstate and sessionstate  What s the difference between overriding and overloading a method  Explain how both are done  What s the difference between protected and internal  What about  protected internal   How do short-circuited operators work  Explain what the StringBuilder class is and why you d want to use it  What s the difference between a static method and a non-static method  What does the  volatile  keyword in C  mean  Explain what happens when you pass a  ref  or  out  parameter into a method  What s the difference between those two keywords  What s a weakreference  When would you want to use one  What s the difference between a DataTable and a DataReader  What s the difference between a value-type and a reference type  What does the  readonly  keyword in C  mean    I think it usually helps to ask your applicants to complete a simple coding exercise such as    Write your own linked list class without using the built-in classes  Write your own hashtable class without using the built-in classes  Write a class that represents a binary tree  Write a method that traverses all nodes of the tree  Write a method to perform a binary search on an array without using built-in methods  Draw a database schema for a blog  Each user only has one blog  each blog has many categories  each category has many posts  and each post can belong to more than one category  Ask your applicant to write queries to pull specific information out    Next  look for specific technical know-how     Event handlers  Create a class with a custom event handler  create another class which hooks onto the custom event handler   XML  Load an XML document and select all of the nodes with properties x  y  and z   Functional programming  Create a function that accepts another function as a parameter  A Map or Fold function works really good for this   Reflection  Write a function which determines if a class has a particular attribute   Regex  Write a regular expression which removes all tags from a block of HTML    None of these are particularly difficult questions for a proficient C  programmer to answer  and they should give you a good idea of your applicants particular strengths  You may also want to work in a few questions code sample that make use of specific design patterns    Edit for clarification     Seems that a lot of people don t understand why I d ask these types of questions  Let me touch on a few peoples comments  I m not quoting directly  but paraphrasing instead      Q  When was the last time anyone used volatiles or weak references   A  When I give technical interviews  I look to see whether a person understands the high-level and low-level features of  NET  Volatiles and weak references are two low-level features provided by  NET -- even if these features aren t used often in practice  answers to these questions are extremely revealing    A good understanding of volatiles demonstrates that a person understands how compiler optimizations change the correctness of code  how threads keep local copies of shared state which may be out of sync at any given time  and is minimally aware of some of the complexities of multithreaded code  A good understanding of weak references demonstrates that a person knows about the intimate details of the garbage collector and how it decides when to free memory  Sure  you could ask candidates  how does a garbage collector work   but asking about weak references gets a much better  more thoughtful reply     NET is a fairly abstract language  but star developers almost always have a deep understanding of the CLR and the low-level details of  NET s runtime     Q  Why would anyone need to implement their own hashtable or linked list   A  I m not implying that the Dictionary class is inferior or that people should roll their own hashtable  This is a basic question which tests whether a person has a minimal understanding of datastructures  Thats what these questions test for  bare minimum understanding   You learn about these hashtables and linked lists on the first day of Data Structures 101  If someone can t write a hashtable or a linked list from scratch  then they have a huge gap in their technical knowledge     Q  Why are these questions so crud-oriented   A  Because the title of this thread is  questions every good  NET developer should know   Every  NET developer begins their career writing crud apps  and 90  of all application development people do for a living is concerned with line-of-business applications   I think questions testing a persons knowledge of line-of-business apps are appropriate in most cases  unless you re looking for developers in very specific niches  such as compiler development  game-engine development  theorem-proving  image processing  etc

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Basic questions include    Whats the difference between an abstract class and interface  When would you want to use them  What s the difference between a left join and an inner join  What s the difference between viewstate and sessionstate  What s the difference between overriding and overloading a method  Explain how both are done  What s the difference between protected and internal  What about  protected internal   How do short-circuited operators work  Explain what the StringBuilder class is and why you d want to use it  What s the difference between a static method and a non-static method  What does the  volatile  keyword in C  mean  Explain what happens when you pass a  ref  or  out  parameter into a method  What s the difference between those two keywords  What s a weakreference  When would you want to use one  What s the difference between a DataTable and a DataReader  What s the difference between a value-type and a reference type  What does the  readonly  keyword in C  mean    I think it usually helps to ask your applicants to complete a simple coding exercise such as    Write your own linked list class without using the built-in classes  Write your own hashtable class without using the built-in classes  Write a class that represents a binary tree  Write a method that traverses all nodes of the tree  Write a method to perform a binary search on an array without using built-in methods  Draw a database schema for a blog  Each user only has one blog  each blog has many categories  each category has many posts  and each post can belong to more than one category  Ask your applicant to write queries to pull specific information out    Next  look for specific technical know-how     Event handlers  Create a class with a custom event handler  create another class which hooks onto the custom event handler   XML  Load an XML document and select all of the nodes with properties x  y  and z   Functional programming  Create a function that accepts another function as a parameter  A Map or Fold function works really good for this   Reflection  Write a function which determines if a class has a particular attribute   Regex  Write a regular expression which removes all tags from a block of HTML    None of these are particularly difficult questions for a proficient C  programmer to answer  and they should give you a good idea of your applicants particular strengths  You may also want to work in a few questions code sample that make use of specific design patterns    Edit for clarification     Seems that a lot of people don t understand why I d ask these types of questions  Let me touch on a few peoples comments  I m not quoting directly  but paraphrasing instead      Q  When was the last time anyone used volatiles or weak references   A  When I give technical interviews  I look to see whether a person understands the high-level and low-level features of  NET  Volatiles and weak references are two low-level features provided by  NET -- even if these features aren t used often in practice  answers to these questions are extremely revealing    A good understanding of volatiles demonstrates that a person understands how compiler optimizations change the correctness of code  how threads keep local copies of shared state which may be out of sync at any given time  and is minimally aware of some of the complexities of multithreaded code  A good understanding of weak references demonstrates that a person knows about the intimate details of the garbage collector and how it decides when to free memory  Sure  you could ask candidates  how does a garbage collector work   but asking about weak references gets a much better  more thoughtful reply     NET is a fairly abstract language  but star developers almost always have a deep understanding of the CLR and the low-level details of  NET s runtime     Q  Why would anyone need to implement their own hashtable or linked list   A  I m not implying that the Dictionary class is inferior or that people should roll their own hashtable  This is a basic question which tests whether a person has a minimal understanding of datastructures  Thats what these questions test for  bare minimum understanding   You learn about these hashtables and linked lists on the first day of Data Structures 101  If someone can t write a hashtable or a linked list from scratch  then they have a huge gap in their technical knowledge     Q  Why are these questions so crud-oriented   A  Because the title of this thread is  questions every good  NET developer should know   Every  NET developer begins their career writing crud apps  and 90  of all application development people do for a living is concerned with line-of-business applications   I think questions testing a persons knowledge of line-of-business apps are appropriate in most cases  unless you re looking for developers in very specific niches  such as compiler development  game-engine development  theorem-proving  image processing  etc

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Martin Fowler prefers design skills over platform knowledge  On the other hand you can ask a question which will show knowledge of design patterns and  NET platform like this    Name design patterns and principles you know and how they are utilized in  NET Framework

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I m with the guys that are looking for problem-solving abilities rather than the sort of thing you can look up and memorise from  101 top  NET interview Qs and As    Just to cite myself as an example  I tend to  know  the things I need to use from day to day   I tend to forget  and later have to re-look up  things that I use rarely   If you wanted to trip me up in an interview  it would be very easy   Nevertheless  I have architected and coded much of the infrastructure for a system that uses identical Business Objects and Data layers for its WinForms and ASP NET incarnations  and our codebase is robust and reusable enough for us to be able to support and develop 20  differently configured versions of the web site  as well as an increasing number  currently 5  of the WinForms application         with a development team of two   I used to work on a team as a tech lead  and my job involved quite a lot of recruiting and interviewing   My most spectacular mistake was hiring a guy that knew more about the technology we were using than all the rest of us put together  including me  and I counted myself as an expert   He knew everything         except how to write code that either met the requirements  or could be understood by anyone except himself   When I eventually persuaded the PM not to renew his contract  every single thing he wrote had to be rewritten   Structure your interviews wisely

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Which of the ASP whatever controls would you ever use in production and why    That will tell you quickly whether your subject has ever actually built and maintained a large project for long enough to get burned by DataGrids and LinkButtons  or whether he s still in the Drag Drop  teach yourself in 21 days  phase    the answer is asp Repeater  asp PlaceHolder  asp Literal  and asp Content

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Here are some I ve used to filter programmers applying for jobs as C  programmers   What s the difference between a reference type and a value type   Explain the IDisposable interface  which C  language construct requires it and how you would implement it   Which exception would you throw if a null is passed as an argument to a method which has a contract that doesn t allow nulls for that parameter

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I think if I were interviewing someone who had LINQ experience  I d possibly just ask them to explain LINQ  If they can explain deferred execution  streaming  the IEnumerable IEnumerator interfaces  foreach  iterator blocks  expression trees  for bonus points  anyway  then they can probably cope with the rest   Admittedly they could be  ok  developers and not  get  LINQ yet - I m really thinking of the case where they ve claimed to know enough LINQ to make it a fair question    In the past I ve asked several of the questions already listed  and a few others    Difference between reference and value types Pass by reference vs pass by value IDisposable and finalizers Strings  immutability  character encodings Floating point Delegates Generics Nullable types

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I will suggest some questions focus on understanding of the programming concepts using dotnet like  What is the difference between managed and unmanaged enviroment   GC pros and cons JIT pros and cons If we need to develop application X can we use dotnet why   this will identify how he see the dotnet   I suggest also to write small methods and ask him to rewrite them with better performance using better dotnet classes or standard ways  Also write inccorrect methods  in terms of any  logical or whatever and ask him to correct them

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A few more    Partial classes  And its limitations  Sealed classes How localization can be done in  NET  Database connectivity Various configuration files Delegates vs events Unmanaged dll access Reflections Generic classes Hottest in  NET 3 5 Unit testing frameworks you have used

User · Answer

This is a bit of a variable question  and not really one you should be able to answer completely now  but one you should be able to answer when appropriate    What does the  NET framework offer to get task X done    Or more specifically    Does the  NET framework include an object that does X    For example  I recently spent a few hours developing an object that is optimized to store an array of Booleans and operate on it  such as doing a collection-wise NOT  OR  XOR  AND  set all values  etc  It wasn t until after I finished writing all my unit tests and tweaking it for the best performance possible that I realized my  BoolArray  object already existed in the  NET framework under the name  BitArray    This can be a tough one to answer since many times the best answer on what object   helpers to use is the one you do not know or fully understand  How wonderful the  NET world would be if everyone actually knew about even the simple StringBuilder  a basic tool that can increase performance significant amounts

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Basic questions include    Whats the difference between an abstract class and interface  When would you want to use them  What s the difference between a left join and an inner join  What s the difference between viewstate and sessionstate  What s the difference between overriding and overloading a method  Explain how both are done  What s the difference between protected and internal  What about  protected internal   How do short-circuited operators work  Explain what the StringBuilder class is and why you d want to use it  What s the difference between a static method and a non-static method  What does the  volatile  keyword in C  mean  Explain what happens when you pass a  ref  or  out  parameter into a method  What s the difference between those two keywords  What s a weakreference  When would you want to use one  What s the difference between a DataTable and a DataReader  What s the difference between a value-type and a reference type  What does the  readonly  keyword in C  mean    I think it usually helps to ask your applicants to complete a simple coding exercise such as    Write your own linked list class without using the built-in classes  Write your own hashtable class without using the built-in classes  Write a class that represents a binary tree  Write a method that traverses all nodes of the tree  Write a method to perform a binary search on an array without using built-in methods  Draw a database schema for a blog  Each user only has one blog  each blog has many categories  each category has many posts  and each post can belong to more than one category  Ask your applicant to write queries to pull specific information out    Next  look for specific technical know-how     Event handlers  Create a class with a custom event handler  create another class which hooks onto the custom event handler   XML  Load an XML document and select all of the nodes with properties x  y  and z   Functional programming  Create a function that accepts another function as a parameter  A Map or Fold function works really good for this   Reflection  Write a function which determines if a class has a particular attribute   Regex  Write a regular expression which removes all tags from a block of HTML    None of these are particularly difficult questions for a proficient C  programmer to answer  and they should give you a good idea of your applicants particular strengths  You may also want to work in a few questions code sample that make use of specific design patterns    Edit for clarification     Seems that a lot of people don t understand why I d ask these types of questions  Let me touch on a few peoples comments  I m not quoting directly  but paraphrasing instead      Q  When was the last time anyone used volatiles or weak references   A  When I give technical interviews  I look to see whether a person understands the high-level and low-level features of  NET  Volatiles and weak references are two low-level features provided by  NET -- even if these features aren t used often in practice  answers to these questions are extremely revealing    A good understanding of volatiles demonstrates that a person understands how compiler optimizations change the correctness of code  how threads keep local copies of shared state which may be out of sync at any given time  and is minimally aware of some of the complexities of multithreaded code  A good understanding of weak references demonstrates that a person knows about the intimate details of the garbage collector and how it decides when to free memory  Sure  you could ask candidates  how does a garbage collector work   but asking about weak references gets a much better  more thoughtful reply     NET is a fairly abstract language  but star developers almost always have a deep understanding of the CLR and the low-level details of  NET s runtime     Q  Why would anyone need to implement their own hashtable or linked list   A  I m not implying that the Dictionary class is inferior or that people should roll their own hashtable  This is a basic question which tests whether a person has a minimal understanding of datastructures  Thats what these questions test for  bare minimum understanding   You learn about these hashtables and linked lists on the first day of Data Structures 101  If someone can t write a hashtable or a linked list from scratch  then they have a huge gap in their technical knowledge     Q  Why are these questions so crud-oriented   A  Because the title of this thread is  questions every good  NET developer should know   Every  NET developer begins their career writing crud apps  and 90  of all application development people do for a living is concerned with line-of-business applications   I think questions testing a persons knowledge of line-of-business apps are appropriate in most cases  unless you re looking for developers in very specific niches  such as compiler development  game-engine development  theorem-proving  image processing  etc

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Good questions I have been asked are    What do you think is good about  NET  What do you think is bad about  NET    It would be interesting to see what a candidate would come up with and you ll certainly learn quite a bit about how he she uses the framework

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A few more   What are the limitations of garbage collection   Know about finalizers and IDisposable   Be aware of the thread pool and when to use it    If you re doing GUI applications - be aware that Windows GUI is single threaded    Use foreach  I see a lot of people doing MoveNext etc

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I found these lists on Scott Hanselman s blog    What Great  NET Developers Ought To Know  More  NET Interview Questions  ASP NET Interview Questions   Here are what I think are the most important questions from these posts divided into categories  I edited and re-arranged them  Fortunately for most of these questions there is already a good answer on Stack Overflow  Just follow the links  I will update them all ASAP    Platform independent  NET questions   What is the difference between a thread and a process  What is the difference between an EXE and a DLL   What is strong-typing versus weak-typing  What is the difference between a Equals b  and a    b  What is boxing  Is string a value type or a reference type   What is the Global Assembly Cache  GAC   What problem does it solve  What is an Interface and how is it different from a Class  What is Reflection  Conceptually  what is the difference between early-binding and late-binding  When would using Assembly LoadFrom or Assembly LoadFile be appropriate  What is an Asssembly Qualified Name  Is it a filename  How is it different  How is a strongly-named assembly different from one that isn   t strongly-named  What does this do  sn -t foo dll  How does the generational garbage collector in the  NET CLR manage object lifetime  What is non-deterministic finalization  What is the difference between Finalize   and Dispose     external article  What is the difference between in-proc and out-of-proc  What technology enables out-of-proc communication in  NET   What is FullTrust  Do GAC   ed assemblies have FullTrust  What is the difference between Debug Write and Trace Write  When should each be used  What is the difference between a Debug and Release build  Is there a significant speed difference  Why or why not  What is the difference between  catch  Exception e   throw e   and catch  Exception e   throw     What is the difference between typeof foo  and myFoo GetType     What is the purpose of XML Namespaces  What is the difference between an XML  Fragment  and an XML  Document    XML Basics  How would you validate XML using  NET     ASP NET   What is a PostBack  What is ViewState  How is it encoded  Is it encrypted  Who uses ViewState  Why is it either useful or evil   What Session State providers are available in ASP NET  What are the pros and cons of each  What is the OO relationship between an ASPX page and its CS VB code behind file  How would one implement ASP NET HTML output caching  caching outgoing versions of pages generated via all values of q  except where q 5  as in http   localhost page aspx q 5   What are HttpHandlers  What are HttpModules  What is needed to configure a new extension for use in ASP NET  For example  what if I wanted my system to serve ASPX files with a   jsp extension  How do cookies work  What is an example of Cookie abuse  What kind of data is passed via HTTP Headers  How does IIS communicate at runtime with ASP NET   Where is ASP NET at runtime in the different versions of IIS  5 to 7

User · Answer

I think if I were interviewing someone who had LINQ experience  I d possibly just ask them to explain LINQ  If they can explain deferred execution  streaming  the IEnumerable IEnumerator interfaces  foreach  iterator blocks  expression trees  for bonus points  anyway  then they can probably cope with the rest   Admittedly they could be  ok  developers and not  get  LINQ yet - I m really thinking of the case where they ve claimed to know enough LINQ to make it a fair question    In the past I ve asked several of the questions already listed  and a few others    Difference between reference and value types Pass by reference vs pass by value IDisposable and finalizers Strings  immutability  character encodings Floating point Delegates Generics Nullable types

User · Answer

I would prefer giving him a problem and asking him to solve it using the features of  net you know and why do you think it is best solution   This will crack almost all the capabilities of a candidate in terms of technical  analytical and problem solving skills along with his approach for solving a problem

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I m with the guys that are looking for problem-solving abilities rather than the sort of thing you can look up and memorise from  101 top  NET interview Qs and As    Just to cite myself as an example  I tend to  know  the things I need to use from day to day   I tend to forget  and later have to re-look up  things that I use rarely   If you wanted to trip me up in an interview  it would be very easy   Nevertheless  I have architected and coded much of the infrastructure for a system that uses identical Business Objects and Data layers for its WinForms and ASP NET incarnations  and our codebase is robust and reusable enough for us to be able to support and develop 20  differently configured versions of the web site  as well as an increasing number  currently 5  of the WinForms application         with a development team of two   I used to work on a team as a tech lead  and my job involved quite a lot of recruiting and interviewing   My most spectacular mistake was hiring a guy that knew more about the technology we were using than all the rest of us put together  including me  and I counted myself as an expert   He knew everything         except how to write code that either met the requirements  or could be understood by anyone except himself   When I eventually persuaded the PM not to renew his contract  every single thing he wrote had to be rewritten   Structure your interviews wisely

User · Answer

Who is Jon Skeet

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I found these lists on Scott Hanselman s blog    What Great  NET Developers Ought To Know  More  NET Interview Questions  ASP NET Interview Questions   Here are what I think are the most important questions from these posts divided into categories  I edited and re-arranged them  Fortunately for most of these questions there is already a good answer on Stack Overflow  Just follow the links  I will update them all ASAP    Platform independent  NET questions   What is the difference between a thread and a process  What is the difference between an EXE and a DLL   What is strong-typing versus weak-typing  What is the difference between a Equals b  and a    b  What is boxing  Is string a value type or a reference type   What is the Global Assembly Cache  GAC   What problem does it solve  What is an Interface and how is it different from a Class  What is Reflection  Conceptually  what is the difference between early-binding and late-binding  When would using Assembly LoadFrom or Assembly LoadFile be appropriate  What is an Asssembly Qualified Name  Is it a filename  How is it different  How is a strongly-named assembly different from one that isn   t strongly-named  What does this do  sn -t foo dll  How does the generational garbage collector in the  NET CLR manage object lifetime  What is non-deterministic finalization  What is the difference between Finalize   and Dispose     external article  What is the difference between in-proc and out-of-proc  What technology enables out-of-proc communication in  NET   What is FullTrust  Do GAC   ed assemblies have FullTrust  What is the difference between Debug Write and Trace Write  When should each be used  What is the difference between a Debug and Release build  Is there a significant speed difference  Why or why not  What is the difference between  catch  Exception e   throw e   and catch  Exception e   throw     What is the difference between typeof foo  and myFoo GetType     What is the purpose of XML Namespaces  What is the difference between an XML  Fragment  and an XML  Document    XML Basics  How would you validate XML using  NET     ASP NET   What is a PostBack  What is ViewState  How is it encoded  Is it encrypted  Who uses ViewState  Why is it either useful or evil   What Session State providers are available in ASP NET  What are the pros and cons of each  What is the OO relationship between an ASPX page and its CS VB code behind file  How would one implement ASP NET HTML output caching  caching outgoing versions of pages generated via all values of q  except where q 5  as in http   localhost page aspx q 5   What are HttpHandlers  What are HttpModules  What is needed to configure a new extension for use in ASP NET  For example  what if I wanted my system to serve ASPX files with a   jsp extension  How do cookies work  What is an example of Cookie abuse  What kind of data is passed via HTTP Headers  How does IIS communicate at runtime with ASP NET   Where is ASP NET at runtime in the different versions of IIS  5 to 7

User · Answer

This is a bit of a variable question  and not really one you should be able to answer completely now  but one you should be able to answer when appropriate    What does the  NET framework offer to get task X done    Or more specifically    Does the  NET framework include an object that does X    For example  I recently spent a few hours developing an object that is optimized to store an array of Booleans and operate on it  such as doing a collection-wise NOT  OR  XOR  AND  set all values  etc  It wasn t until after I finished writing all my unit tests and tweaking it for the best performance possible that I realized my  BoolArray  object already existed in the  NET framework under the name  BitArray    This can be a tough one to answer since many times the best answer on what object   helpers to use is the one you do not know or fully understand  How wonderful the  NET world would be if everyone actually knew about even the simple StringBuilder  a basic tool that can increase performance significant amounts

User · Answer

I suggest enquiring about blogs that they read on a regular basis and personal programming projects that they  have worked on as this will show a willingness to learn and a passion for programming

User · Answer

Good questions I have been asked are    What do you think is good about  NET  What do you think is bad about  NET    It would be interesting to see what a candidate would come up with and you ll certainly learn quite a bit about how he she uses the framework

User · Answer

I d not ask those  know something from the textbook  questions  but rather ask some tinkering stuff like     What does the foreach loop do in plain C    Expecting him to write a iterator loop   What s a singleton  Let him her parse a String to Datetime  expecting him her to use TryParse instead of try catch  Implement the singleton  strategy and command patterns Let him her Refactor a piece of code for testing  Expecting him her to abstract the external services away from the Unit under Test and implement his own Test-double of the service  providing no mocking framework    These are not 100  sure  depending on the person I may ask them    let him her guard a method from null input  expecting him her to use multiple returns to reduce nesting  how does a object initializer work  Expecting him her to write the thread-safe assignment    Also I d ask him how he she learned his her stuff and what he she is reading  what blogs  books

User · Answer

What is a thread    What is the GC

User · Answer

I think if I were interviewing someone who had LINQ experience  I d possibly just ask them to explain LINQ  If they can explain deferred execution  streaming  the IEnumerable IEnumerator interfaces  foreach  iterator blocks  expression trees  for bonus points  anyway  then they can probably cope with the rest   Admittedly they could be  ok  developers and not  get  LINQ yet - I m really thinking of the case where they ve claimed to know enough LINQ to make it a fair question    In the past I ve asked several of the questions already listed  and a few others    Difference between reference and value types Pass by reference vs pass by value IDisposable and finalizers Strings  immutability  character encodings Floating point Delegates Generics Nullable types

User · Answer

Martin Fowler prefers design skills over platform knowledge  On the other hand you can ask a question which will show knowledge of design patterns and  NET platform like this    Name design patterns and principles you know and how they are utilized in  NET Framework

User · Answer

Know the difference between reference and value types   Know that events are stored as hard references  i e  remember to unregister events or the application will leak memory    Strings are immutable

User · Answer

A few more    Partial classes  And its limitations  Sealed classes How localization can be done in  NET  Database connectivity Various configuration files Delegates vs events Unmanaged dll access Reflections Generic classes Hottest in  NET 3 5 Unit testing frameworks you have used

User · Answer

What is a thread    What is the GC

User · Answer

I d not ask those  know something from the textbook  questions  but rather ask some tinkering stuff like     What does the foreach loop do in plain C    Expecting him to write a iterator loop   What s a singleton  Let him her parse a String to Datetime  expecting him her to use TryParse instead of try catch  Implement the singleton  strategy and command patterns Let him her Refactor a piece of code for testing  Expecting him her to abstract the external services away from the Unit under Test and implement his own Test-double of the service  providing no mocking framework    These are not 100  sure  depending on the person I may ask them    let him her guard a method from null input  expecting him her to use multiple returns to reduce nesting  how does a object initializer work  Expecting him her to write the thread-safe assignment    Also I d ask him how he she learned his her stuff and what he she is reading  what blogs  books

User · Answer

A few more   What are the limitations of garbage collection   Know about finalizers and IDisposable   Be aware of the thread pool and when to use it    If you re doing GUI applications - be aware that Windows GUI is single threaded    Use foreach  I see a lot of people doing MoveNext etc

User · Answer

I m with the guys that are looking for problem-solving abilities rather than the sort of thing you can look up and memorise from  101 top  NET interview Qs and As    Just to cite myself as an example  I tend to  know  the things I need to use from day to day   I tend to forget  and later have to re-look up  things that I use rarely   If you wanted to trip me up in an interview  it would be very easy   Nevertheless  I have architected and coded much of the infrastructure for a system that uses identical Business Objects and Data layers for its WinForms and ASP NET incarnations  and our codebase is robust and reusable enough for us to be able to support and develop 20  differently configured versions of the web site  as well as an increasing number  currently 5  of the WinForms application         with a development team of two   I used to work on a team as a tech lead  and my job involved quite a lot of recruiting and interviewing   My most spectacular mistake was hiring a guy that knew more about the technology we were using than all the rest of us put together  including me  and I counted myself as an expert   He knew everything         except how to write code that either met the requirements  or could be understood by anyone except himself   When I eventually persuaded the PM not to renew his contract  every single thing he wrote had to be rewritten   Structure your interviews wisely

User · Answer

I will suggest some questions focus on understanding of the programming concepts using dotnet like  What is the difference between managed and unmanaged enviroment   GC pros and cons JIT pros and cons If we need to develop application X can we use dotnet why   this will identify how he see the dotnet   I suggest also to write small methods and ask him to rewrite them with better performance using better dotnet classes or standard ways  Also write inccorrect methods  in terms of any  logical or whatever and ask him to correct them

User · Answer

I will suggest some questions focus on understanding of the programming concepts using dotnet like  What is the difference between managed and unmanaged enviroment   GC pros and cons JIT pros and cons If we need to develop application X can we use dotnet why   this will identify how he see the dotnet   I suggest also to write small methods and ask him to rewrite them with better performance using better dotnet classes or standard ways  Also write inccorrect methods  in terms of any  logical or whatever and ask him to correct them

User · Answer

This might not be what you want to hear  but I would recommend not focusing on narrow technologies  but on general programming and problem solving skills  Solid developers can learn whatever you want them to do quickly    I  for instance  am not a Compact Framework guy  so I might fail your interview if you went that direction  But if I needed to use it I could do some research and jump right in   Joel s book  Smart and Gets Things Done  has great advice for hiring devs and there are large juicy sections about the kinds of questions to ask  I highly recommend it

User · Answer

I will suggest some questions focus on understanding of the programming concepts using dotnet like  What is the difference between managed and unmanaged enviroment   GC pros and cons JIT pros and cons If we need to develop application X can we use dotnet why   this will identify how he see the dotnet   I suggest also to write small methods and ask him to rewrite them with better performance using better dotnet classes or standard ways  Also write inccorrect methods  in terms of any  logical or whatever and ask him to correct them

User · Answer

This is a bit of a variable question  and not really one you should be able to answer completely now  but one you should be able to answer when appropriate    What does the  NET framework offer to get task X done    Or more specifically    Does the  NET framework include an object that does X    For example  I recently spent a few hours developing an object that is optimized to store an array of Booleans and operate on it  such as doing a collection-wise NOT  OR  XOR  AND  set all values  etc  It wasn t until after I finished writing all my unit tests and tweaking it for the best performance possible that I realized my  BoolArray  object already existed in the  NET framework under the name  BitArray    This can be a tough one to answer since many times the best answer on what object   helpers to use is the one you do not know or fully understand  How wonderful the  NET world would be if everyone actually knew about even the simple StringBuilder  a basic tool that can increase performance significant amounts

User · Answer

I would always look for the soft skills myself - no pun intended  So good OO design  test driven development  a good multi  programming  lingual background and all round general smartness  and getting-things done-ness I guess     An intelligent developer should not have any trouble learning the individual technologies that you need them to know even if they have never looked at them before - so I wouldn t worry too much about specific questions around WCF compact framework and the like   I would have them write some code - best way to find out what they know and how they work  Anyone can memorise the answer to  What s the difference between a reference type and a value type

User · Answer

This might not be what you want to hear  but I would recommend not focusing on narrow technologies  but on general programming and problem solving skills  Solid developers can learn whatever you want them to do quickly    I  for instance  am not a Compact Framework guy  so I might fail your interview if you went that direction  But if I needed to use it I could do some research and jump right in   Joel s book  Smart and Gets Things Done  has great advice for hiring devs and there are large juicy sections about the kinds of questions to ask  I highly recommend it

User · Answer

I think it shouldn t be just questions  I know a few guys who are brilliant when you interview them but once they get to the real thing they are too much perfectionist I would say that they fail to code the task miserably    I ve been once interviewed and I kinda liked the approach where first employer gave me a technical questionnaire to fill in 30 minutes  If one is successful then he ll be called for a 1 hour interview covering Personality Judgement and Character finding questions plus technical jargons   Then I ve been asked to develop a three page web application in 6 hours time  The constraints impose in application was smartly covering major aspect of application development like a small ERD  Layerd Design  UI Consistency  controls specific problems like using Radio buttons in GridView and Fetching and displaying image types from DB on a web page  one algorithm development  security  Encryption  Hashing  Data representation and manipulation    Then Next day they followed by a 30 minutes discussion on the developed application covering performance bottleneck areas and improvements on design and used algorithms  And 1 hour optional test to improve your algorithm developed in previous step with a specific condition   So it took a fair amount of time but this way you can make sure that the person you are hiring knows at-least those concepts which are essential for a good developer to be

User · Answer

This is interesting  and at the risk of getting this down-voted for putting in my opinion  as I am born deaf  being asked a question like that would require more effort in communicating my thoughts on my part personally    To be blunt  I really would not read too much of the typical questions  as the underlying paradigm is  How well can you vocalize your thoughts and understanding    that is really what the interviewer is looking for  Communicating is always my biggest weakness due to the way I am and can get frustrated quite easily   It would be ideal to have the knowledge and be the know-it-all type but unfortunately  there are some things I don t know  but not to be afraid if you actually don t know the answer and admit it rather than bluff through it  If an interviewer asked me a question like one of the above  that I would not be sure of or mis-understand mis-interpret the question  I would say it upfront  which can personally be embarrassing  but have learnt to handle that   You would be surprised at how many would actually waffle on and bluff through it in which at the end of the day get caught out with their  pants down  metaphorically speaking   My 2cents  Best regards  Tom

User · Answer

Know the difference between reference and value types   Know that events are stored as hard references  i e  remember to unregister events or the application will leak memory    Strings are immutable

User · Answer

I think if I were interviewing someone who had LINQ experience  I d possibly just ask them to explain LINQ  If they can explain deferred execution  streaming  the IEnumerable IEnumerator interfaces  foreach  iterator blocks  expression trees  for bonus points  anyway  then they can probably cope with the rest   Admittedly they could be  ok  developers and not  get  LINQ yet - I m really thinking of the case where they ve claimed to know enough LINQ to make it a fair question    In the past I ve asked several of the questions already listed  and a few others    Difference between reference and value types Pass by reference vs pass by value IDisposable and finalizers Strings  immutability  character encodings Floating point Delegates Generics Nullable types

User · Answer

Who is Jon Skeet

User · Answer

I found these lists on Scott Hanselman s blog    What Great  NET Developers Ought To Know  More  NET Interview Questions  ASP NET Interview Questions   Here are what I think are the most important questions from these posts divided into categories  I edited and re-arranged them  Fortunately for most of these questions there is already a good answer on Stack Overflow  Just follow the links  I will update them all ASAP    Platform independent  NET questions   What is the difference between a thread and a process  What is the difference between an EXE and a DLL   What is strong-typing versus weak-typing  What is the difference between a Equals b  and a    b  What is boxing  Is string a value type or a reference type   What is the Global Assembly Cache  GAC   What problem does it solve  What is an Interface and how is it different from a Class  What is Reflection  Conceptually  what is the difference between early-binding and late-binding  When would using Assembly LoadFrom or Assembly LoadFile be appropriate  What is an Asssembly Qualified Name  Is it a filename  How is it different  How is a strongly-named assembly different from one that isn   t strongly-named  What does this do  sn -t foo dll  How does the generational garbage collector in the  NET CLR manage object lifetime  What is non-deterministic finalization  What is the difference between Finalize   and Dispose     external article  What is the difference between in-proc and out-of-proc  What technology enables out-of-proc communication in  NET   What is FullTrust  Do GAC   ed assemblies have FullTrust  What is the difference between Debug Write and Trace Write  When should each be used  What is the difference between a Debug and Release build  Is there a significant speed difference  Why or why not  What is the difference between  catch  Exception e   throw e   and catch  Exception e   throw     What is the difference between typeof foo  and myFoo GetType     What is the purpose of XML Namespaces  What is the difference between an XML  Fragment  and an XML  Document    XML Basics  How would you validate XML using  NET     ASP NET   What is a PostBack  What is ViewState  How is it encoded  Is it encrypted  Who uses ViewState  Why is it either useful or evil   What Session State providers are available in ASP NET  What are the pros and cons of each  What is the OO relationship between an ASPX page and its CS VB code behind file  How would one implement ASP NET HTML output caching  caching outgoing versions of pages generated via all values of q  except where q 5  as in http   localhost page aspx q 5   What are HttpHandlers  What are HttpModules  What is needed to configure a new extension for use in ASP NET  For example  what if I wanted my system to serve ASPX files with a   jsp extension  How do cookies work  What is an example of Cookie abuse  What kind of data is passed via HTTP Headers  How does IIS communicate at runtime with ASP NET   Where is ASP NET at runtime in the different versions of IIS  5 to 7

User · Answer

Good questions I have been asked are    What do you think is good about  NET  What do you think is bad about  NET    It would be interesting to see what a candidate would come up with and you ll certainly learn quite a bit about how he she uses the framework

User · Answer

I would prefer giving him a problem and asking him to solve it using the features of  net you know and why do you think it is best solution   This will crack almost all the capabilities of a candidate in terms of technical  analytical and problem solving skills along with his approach for solving a problem

User · Answer

Which of the ASP whatever controls would you ever use in production and why    That will tell you quickly whether your subject has ever actually built and maintained a large project for long enough to get burned by DataGrids and LinkButtons  or whether he s still in the Drag Drop  teach yourself in 21 days  phase    the answer is asp Repeater  asp PlaceHolder  asp Literal  and asp Content

User · Answer

I d not ask those  know something from the textbook  questions  but rather ask some tinkering stuff like     What does the foreach loop do in plain C    Expecting him to write a iterator loop   What s a singleton  Let him her parse a String to Datetime  expecting him her to use TryParse instead of try catch  Implement the singleton  strategy and command patterns Let him her Refactor a piece of code for testing  Expecting him her to abstract the external services away from the Unit under Test and implement his own Test-double of the service  providing no mocking framework    These are not 100  sure  depending on the person I may ask them    let him her guard a method from null input  expecting him her to use multiple returns to reduce nesting  how does a object initializer work  Expecting him her to write the thread-safe assignment    Also I d ask him how he she learned his her stuff and what he she is reading  what blogs  books

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