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[.net] Questions every good .NET developer should be able to answer?

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...).

alt text

*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.

This question is related to .net

The answer is

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.

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.

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.

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.

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

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...

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.

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?

I found these lists on Scott Hanselman's blog:

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

ASP.NET

"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)

I found these lists on Scott Hanselman's blog:

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

ASP.NET

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?

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

What is a thread?

What is the GC?

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.

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?

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.

I found these lists on Scott Hanselman's blog:

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

ASP.NET

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?'

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.

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.

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.

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?

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?'

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.

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

Who is Jon Skeet?

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?

What is a thread?

What is the GC?

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?

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.

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).

I found these lists on Scott Hanselman's blog:

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

ASP.NET

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.)

Who is Jon Skeet?

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...

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.

"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)

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.)

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.

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.

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.

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.

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?

Who is Jon Skeet?

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?

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.

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?'

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.

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).

What is a thread?

What is the GC?

Who is Jon Skeet?

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).

A few more:

  1. Partial classes. And its limitations?
  2. Sealed classes
  3. How localization can be done in .NET?
  4. Database connectivity
  5. Various configuration files
  6. Delegates vs events
  7. Unmanaged dll access
  8. Reflections
  9. Generic classes
  10. Hottest in .NET 3.5
  11. Unit testing frameworks you have used.

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.)

A few more:

  1. Partial classes. And its limitations?
  2. Sealed classes
  3. How localization can be done in .NET?
  4. Database connectivity
  5. Various configuration files
  6. Delegates vs events
  7. Unmanaged dll access
  8. Reflections
  9. Generic classes
  10. Hottest in .NET 3.5
  11. Unit testing frameworks you have used.

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."

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.)

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...

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.

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.

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.

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.

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).

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."

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?'

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.

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.

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...

What is a thread?

What is the GC?

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.

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."

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?

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

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.

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."

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.

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?

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.

Source: Stackoverflow.com

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