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Quick Tip - Sharing code between multiple projects in Visual Studio 2005

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I have long been an advocate for putting common code into an assembly that is shared by applications needing the functionality.  That said, there are times where the separate assembly approach is not appropriate.  For those situations, today's tip may help make code sharing easier.

I have a project (called TestApp) that targets the .NET Compact Framework version 2.  In the TestApp project, there is a file called Helper.cs which implements a class containing static methods that I use throughout the TestApp project.

While working on TestApp, I decide that a .NET Framework (for desktop PCs) version would be nice to have.  Since I already have Helper.cs written, I would like to use the existing version.  I had previously chosen to not use an assembly for these helpers, so I add the existing file to my new project. 

I would prefer to not create a duplicate of this file as maintaining changes between the two copies can be time consuming and error prone.  Fortunately, Visual Studio 2005 has a great feature to allow for file sharing between projects -- you can add an existing file as a link.  Here's how:

  1. In the project where you wish to add the file, right click the project name in the Solution Explorer
  2. Select Add and then Existing Item...
  3. In the Add Existing Item dialog, navigate to the desired file
  4. Click the downward pointing arrow next to the Add button and select Add As Link.
    Once added to a project, linked files are easy to identify by the small arrow in the lower-left corner of the file icon in the Solution Explorer.

My new project now has a reference to the original Helper.cs and any changes I make to it, from either project, are reflected in both projects.

Note: It is important to remember that if you are sharing a file between different versions of the .NET Framework, you need to verify that any changes made are compatible with all projects using the file.

Enjoy!
-- DK

Disclaimer(s):
This posting is provided "AS IS" with no warranties, and confers no rights.

Comments

  • Anonymous
    December 02, 2006
    It seems like this would have an adverse effect on the ease of sharing projects between developers, as it would require, potentially, having to acquire additional projects that perhaps you really don't care about. I think I'd honestly prefer doing the extra work of moving that file into it's own assembly over linking to a file in a potentially unrelated project. Or, at a minimum, moving it to it's own, separate folder, and linking to it from both projects, instead of reaching from one project into another.

    David Kline: In the case of sharing projects, a separate assembly is my preference as well.  I typically use file links for simple, small projects where I am the only developer.

  • Anonymous
    December 02, 2006
    Just wondering does this work well with TFS Build?

  • Anonymous
    December 12, 2006
    Does the shared file required to be a part of a project. Because I have an instance where my C# file will not be a part of the project but it is a generated file and then many projects utlize the same file. Now I tried the same approach of Add as Link but the VSS does not reflect the link file. How do I achieve that since I am using VSS 2005 and not VSTS?