The "Copy Local" Bug in Visual Studio

If you've ever worked with me on a Microsoft Office SharePoint Server (MOSS) 2007 project -- or if you've read my Sample Walkthrough of the DR.DADA Approach to SharePoint -- then you've probably seen the following comment:

Note: Referenced assemblies must be specified with a path corresponding to the build configuration. If the path is not specified to the referenced assembly, then the build works fine as long as the referenced assembly is not in the GAC.

However, when the referenced assembly is in the GAC (i.e. after a deployment) then MakeCAB will not be able to find the referenced assembly (since it is no longer copied to the current project's bin\Debug or bin\Release folder).

It turns out that I was using a rather elaborate workaround for a problem that is actually much easier to solve.

To workaround the "Copy Local" bug and force a referenced assembly to always be copied to the output folder (regardless of whether the referenced assembly is in the GAC):

  1. In the Solution Explorer window in Visual Studio, expand the References folder for the project and then select the referenced assembly.
  2. In the Properties window, change the value of Copy Local to False, and then change it back to True.

Following these two simple steps explicitly adds <Private>True</Private> to the project file, as shown in the following example:

     <ProjectReference Include="..\CoreServices\CoreServices.csproj">
      <Name>CoreServices %28CoreServices\CoreServices%29</Name>

When you add a referenced assembly in Visual Studio using a project reference, Copy Local defaults to True, but Visual Studio doesn't explicitly state this in the MSBuild project file. Toggling the value of Copy Local forces this element to be added to the project file and consequently you no longer need any hacks to reference the assembly in its original output folder.

At this point, you might be wondering why do I bring this up after all this time? After all, hasn't the hack I came up with for building SharePoint Web Solution Packages (WSPs) been working for several years? Well, yes, in most cases it works just fine.

However, there's one fundamental problem that I only recently discovered back in early October: you can't use Team Foundation Build to build the WSP when specifying relative paths to assemblies in the DDF file.

I'll cover this in my next post.