How to use a class from one C project with another C project

Question

In the same solution  I have two projects  P1 and P2  How can I make use of a class of P1 in P2

User · Answer

Say your class in project 2 is called MyClass.

Obviously, first reference your project 2 under references in project 1 then

using namespaceOfProject2;

// for the class calling bit:

namespaceOfProject2.MyClass project2Class = new namespaceOfProject2.MyClass();

so whenever you want to reference that class you type project2Class. Plus make sure that class is public too.

User · Answer

I had an issue with different target frameworks    I was doing everything right  but just couldn t use the reference in P2   After I set the same target framework for P1 and P2  it worked like a charm   Hope it will help someone

User · Answer

The first step is to make P2 reference P1 by doing the following   Right Click on the project and select  Add Reference  Go to the Projects Tab Select P1 and hit OK   Next you ll need to make sure that the classes in P1 are accessible to P2   The easiest way is to make them public     public class MyType           Now you should be able to use them in P2 via their fully qualified name   Assuming the namespace of P1 is Project1 then the following would work  Project1 MyType obj   new Project1 MyType      The preferred way though is to add a using for Project1 so you can use the types without qualification  using Project1       public void Example       MyType obj   new MyType

User · Answer

Simply add reference to P1 from P2

User · Answer

All too often a new developer asks this simple question which is a common problem specifically with Visual Studio IDE s  Few people answer the specific question and often critique the question or give  guesses  for solutions which don t answer the common problems  The first common problem is the IDE leads you to create new projects rather than add new files   java   py   cpp   c  to the existing solution  by default it creates a new solution  unless you change the project name and add to the current solution  This problem occurs for Python  java  c   C   and C project folders   The new developer selecting  new project project name and changing the solution directory to  use same solution  still creates a new  project  in the same solution space  but not in the same directory space as the current user interface file or command line file which still leads to problems with  package not found  errors when building and running the project or solution   This is why the above coding suggestions to importing packages  classes  methods and functions only work  and thus don t answer the question  when the  library  file or  separate behavior  file is not only in the same solution directory path  but also in the same  user interface  or  command shell  application directory space  This does does not happen when you add another project using the new project project type commands of the IDE  The problem here is the new project is stored in a different directory than the existing Client or User interface code files   To create a new  file  in the same project space rather than new project the beginner needs to do the following that Microsoft won t do for you and even misleads you away from the intuitively obvious by default     Select the  application  you want to import the new behavior into  from another file  Select project add new item Select the  program file template type  such as filetype py  filetype java  filetype c  filetype cpp  filetype C   etc  or a library class file type  something other than startup file options you see when you create a new application project or create a new library project   A new file name with default name is created in your project  Change the default name of the file to something like library py or fa  ade java  etc    NOW the code recommendations to import libraries or using namespaces will work as described in the comments above and you don t have to change path statements or change solutions paths and solution names that Microsoft won t let you change easily  i e  you can change the filenames or project names but the IDE won t automatically change the project path or the solution path names    The following is a Python example but works similar for C   java  or C C   using the includes  namespaces or using code commands appropriate to each language to find code in other classes projects in the SAME DIRECTORY SPACE   The application file  hello world  importing from other code files in the same directory   Note the python white space delimiters are not going to space correctly in this stackoverflow comment editor   print   test    from CIXMPythonFacade import ClassA  c1 ClassA c1 methodA    from CIXMPythonFacade import functionA   functionA     class ClassName object             def   init   object  parameter            object parameter   value   The library file or  fa  ade  file containing classes  methods or functions you want to import   class class1 object          description of class     class ClassA object       print   test2       def methodA            print   test3    def functionA         print   test4       return  0    pass   NOW how do you actually solve the mess that the IDE leads you into   To import code from another file in the same directory space you add a reference to it    Select the application file Select Project add reference Choose the filename visible with the right directory path  check it  The reference is now available to the interpreter  the code checker and or the compiler    OK so now that you have this problem solved  how do you really link two separate projects together in the same solution space    You have to go to both the indexer or  intellisense  options and the compiler interpreter and physically check or change add the directory path statements if they are something other than what points to your  second  project or solution space   When you do the path changes or change the path variables to your workspace and to the specific locations of the projects which are different directory spaces the compiler and the code analyzer can then find these libraries  headers h  namespaces  project or file locations  To remove old projects you created by mistake it is even worse   You have to exit the Visual Studio IDE  open windows explorer  go to the workspace directory     documents visualstudio xxx solutionname packagename select the file or folder  right click and  delete  file or folder  When you re-enter the IDE and select open solution or open package solution  the old files and solution package names are gone as are their misleading path statements which fools the compiler and code analyzer to look at the old directory even though you changed the filename and changed the project name  it does not change the directory path with it    Microsoft really  really needs to fix these problem so you can intuitively create what most people want to create as new files in the same directories and remove solutions by selecting them and deleting them from the IDE   Beginners get so frustrated with directory path statements so flexible for seasoned developers  but so unfair to new developers in their defaults   Hope this really helps you new guys and stops seasoned developers from giving you the wrong answers that don t work for you   They assume you already understand path statements and just want to type the right code   which is also why the tunnel in on trying to correct your code but does not help you fix the problem   This is probably the most common problem continually described on stackoverflow with wrong answers that don t work for new programmers

User · Answer

In the  Solution Explorer  tree  expand the P2 project and then right-click the project and select  Add Reference  from the menu  On the  Add Reference  dialog  select the  Projects  tab and select your P1 project    If you are using namespaces then you will need to import the namespaces for your P1 types by adding  using  statements to your files in P2    Note that the types in P1 that you wish to access directly must have a sufficient access level  typically this means they must be made public

User · Answer

To provide another much simpler solution -  Within the project  right click and select  quot Add - gt  Existing quot  Navigate to the class file in the adjacent project  The Add button is also a dropdown  click the dropdown and select   quot Add as link quot  Thats it

User · Answer

In project P1 make the class public  if it isn t already   Then add a project reference  rather than a file reference  a mistake I ve come across occasionally  to P2  Add a using statement in P2 at the correct place and start using the class from P1    To mention this  The alternative to making the class public would be to make P2 a friend to P1  This is  however  unlikely to be the answer you are after as it would have some consequences  So stick with the above suggestion

User · Answer

If you have two projects in one solution folder Just add the Reference of the Project into another using the Namespace you can get the classes  While Creating the object for that the requried class  Call the Method which you want   FirstProject   class FirstClass        public string Name              return  James            Here add reference to the Second Project  SecondProject   class SeccondClass       FirstProject FirstClass obj new FirstProject FirstClass        obj Name

User · Answer

Paul Ruane is correct  I have just tried myself building the project  I just made a whole SLN to test if it worked   I made this in VC  VS2008   lt  lt    Just helping other people that read this aswell with      comments      Step1   Make solution called DoubleProject  Step2   Make Project in solution named DoubleProjectTwo  to do this select the solution file  right click --  Add --  New Project   I now have two project in the same solution  Step3   As Paul Ruane stated  go to references in the solution explorer  if closed it s in the view tab of the compiler   DoubleProjectTwo is the one needing functions methods of DoubleProject so in DoubleProjectTwo right mouse reference there --  Add --  Projects --  DoubleProject   Step4      Include the directive for the   namespace    using System  using System Collections Generic  using System Linq  using System Text  using DoubleProject   lt ------------------------------------------  namespace DoubleProjectTwo       class ClassB               public string textB    I am in Class B Project Two           ClassA classA   new ClassA              public void read                         textB   classA read                        Step5      Make something show me proof of   results    using System  using System Collections Generic  using System Linq  using System Text   namespace DoubleProject       public class ClassA       lt ---------- PUBLIC class               private const string textA    I am in Class A Project One            public string read                         return textA                         The main   using System  using System Collections Generic  using System Linq  using System Text  using DoubleProjectTwo      lt ----- to use ClassB in the main  namespace DoubleProject       class Program               static void Main string   args                        ClassB foo   new ClassB                 Console WriteLine foo textB               Console ReadLine                        That SHOULD do the trick  Hope this helps  EDIT    whoops forgot the method call to actually change the string   don t do the same

[c#] How to use a class from one C# project with another C# project

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