I’m working on a Visual Studio .NET add-in project where we need to be able to build the project both through the Visual Studio IDE and through NAnt.

So I’ve got NAnt 0.84, which builds all the other projects (using the <solution> task) I’ve got just fine, but gives me this error: System.NullReferenceException: Object reference not set to an instance of an object. at NAnt.VSNet.Reference..ctor(Solution solution, ProjectSettings ps, XmlElement elemReference, SolutionTask solutionTask, String outputDir)...

And so on, tracing down the whole call stack. What’s the deal?

As you (probably) know, references in a .csproj file look like this:

<VisualStudioProject>  <CSHARP>   <Build>    <References>     <Reference      Name = "EnvDTE"      AssemblyName = "EnvDTE"      HintPath = "..\..\..\..\..\WINDOWS\Microsoft.NET\Framework\v1.1.4322\EnvDTE.dll"     />    </References>   </Build>  </CSHARP> </VisualStudioProject>

Of course, the “HintPath” attribute is optional.

Apparently it’s not an option for NAnt. The add-in wizard doesn’t put HintPath in for your references, and regardless of what you do, NAnt won’t build without it. (Yes, I added <assemblyfolders> attributes to the <solution> task - you need those, too, but it doesn’t fix it.) So manually edit your .csproj, add the HintPath, and you’re in.