At my current position, I’ve been doing quite a bit of Silverlight development and have also been working with TFS2010 build services to enable continuous integration.  One of the critical pieces of a successful continuous build setup (and also one of the benefits of having one) is that the build system should be able to “get latest” against the source repository and immediately build with no errors.  This can break down both in an automated build scenario and a “new guy” scenario when the solution has external dependencies that may not be present in the build environment.

The method that I use to address the dependency issue is to store all of the binaries upon which my solution depends in a folder under the solution root called “Reference Items”.  I keep this folder as part of the solution and check all of the binaries into source control so when I get the latest version of the solution from source control all of the binaries are downloaded to my machine as well and gets me closer to the ideal where a new developer installs the development IDE, get latest and can immediately build and run unit tests before jumping into coding the feature of the day.

This all sounds pretty good (and it is), but a little while back I ran into one of those little hiccups that requires a little manual intervention.  The issue that I ran into is that with Silverlight (at least version 4), the behavior of the “Add Reference” command when adding reference to a DLL that is present in the GAC is to omit the HintPath element that it includes with regular .Net projects, so even if the DLL is setting in the Reference Items folder and downloaded to the build machine it cannot be found at compile time and the build will fail.

To work around this behavior, you need to be comfortable editing the XML project files generated by Visual Studio (in my case this is typically a .csproj file).  Simply open the project file in your favorite text editor, find the Reference element that refers to the component, and modify the XML to include the HintPath.  Here’s a before and after example of the component that ultimately led me to the investigation behind this post:

Before:
<Reference Include="Telerik.Windows.Controls, Version=2011.2.920.1040, Culture=neutral, PublicKeyToken=5803cfa389c90ce7, processorArchitecture=MSIL" />

After:
<Reference Include="Telerik.Windows.Controls, Version=2011.2.920.1040, Culture=neutral, PublicKeyToken=5803cfa389c90ce7, processorArchitecture=MSIL">
      <HintPath>..\Reference Items\Telerik.Windows.Controls.dll</HintPath>
    </Reference>