this.Pose() as Expert

Wednesday, 23 July 2008

I have created another (hopefully useful) checkin policy for Team Foundation Server 2008 - one that checks C# and VB.NET project files for COM references. The idea came from a customer, where they require the developers to use "authorized" interop assemblies instead of developers recreating those by simply adding a COM reference to each and every project. And how do you prevent this? By having a TFS checkin policy in place.

A COM reference looks like this in an MSBuild project file:

<ItemGroup>
    <COMReference Include="XcpControlLib">
      <Guid>{283C8576-0726-4DBC-9609-3F855162009A}</Guid>
      <VersionMajor>1</VersionMajor>
      <VersionMinor>0</VersionMinor>
      <Lcid>0</Lcid>
      <WrapperTool>tlbimp</WrapperTool>
      <Isolated>False</Isolated>
    </COMReference>
</ItemGroup>

Instead of searching for the string "<COMReference" I decided to use the MSBuild Engine API in my implementation:

    public override PolicyFailure[] Evaluate()
    {
      PendingChange[] checkedFiles = PendingCheckin.PendingChanges.CheckedPendingChanges;
      ArrayList failures = new ArrayList();

      foreach (PendingChange change in checkedFiles)
      {
        string extension = Path.GetExtension(change.LocalItem);

        if ((0 == String.Compare(extension, ".csproj", false)) ||
            (0 == String.Compare(extension, ".vbproj", false)))
        {
          if (change.ChangeType == ChangeType.Edit || change.ChangeType == ChangeType.Add)
          {
            // this is a workaround because project.Load(fileName doesn't work in the same process as VS
            FileStream fs = File.OpenRead(change.LocalItem);

            Project project = new Project();
            project.Load(new StreamReader(fs), ProjectLoadSettings.IgnoreMissingImports);

            foreach (BuildItemGroup big in project.ItemGroups)
            {
              foreach (BuildItem bi in big)
              {
                if (0 == String.Compare(bi.Name, "COMReference", true))
                {
                  PolicyFailure failure = new PolicyFailure(String.Format(ComReferencePolicyStrings.activateMessage, change.LocalItem), this);
                  failures.Add(failure);
                }
              }
            }
          }
        }
      }

      return (PolicyFailure[])failures.ToArray(typeof(PolicyFailure));
    }

At first, I tried to load directly from the .??proj files, but Visual Studio (after thinking a bit about it it is pretty obvious...) doesn't like someone inside its process play around with the MSBuild engine. That's why I resorted to loading it indirectly.

For installation I have provided checkinpolicy.reg, however, you must adapt the path to the .dll before importing it into the registry.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\9.0\TeamFoundation\SourceControl\Checkin Policies]
"ChrisOnNet.CheckinPolicies.ComReferencePolicy"="C:\\Work\\ChrisOnNet.CheckinPolicies.ComReferencePolicy.dll"

Once registered, you can add it to your team projects: