This is a weird one. When unfolding t4 templates, NuPattern tries to close windows that might have been opened when adding a file (https://github.com/NuPattern/NuPattern/blob/be18383399bf1db558e52dd98e9af40a6fc45807/Src/Common/Source/Common.VisualStudio/Solution/VsFileTemplate.cs#L67-74)

                //
                // The file may have opened anyway, if we're not supposed to open it, we'll search for
                // the matching window and close it
                //
                foreach (EnvDTE.Window w in container.DTE.Windows)
                {
                    if (newlyAddedFile.Equals(w.ProjectItem))
                    {
                        w.Close(EnvDTE.vsSaveChanges.vsSaveChangesNo);
                        break;
                    }
                }

If one of the open windows is a Project Properties page, asking the window for its ProjectItem throws an InvalidCastException.

Repro steps with the MVC sample:

1. Create a new app
2. Build.
3. Open the properties of the MVC app project
4. While the property page is still open, add a controller.

You'll get an error:

NuPattern.Library.Automation.EventAutomation Error: 0 : Event automation 'GenerateControllerOnInstantiate' failed.
System.InvalidCastException: Unable to cast COM object of type 'System.__ComObject' to interface type 'EnvDTE.ProjectItem'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{0B48100A-473E-433C-AB8F-66B9739AB620}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).
   at Microsoft.VisualStudio.Platform.WindowManagement.DTE.Window.get_ProjectItem()
   at Microsoft.VisualStudio.Platform.WindowManagement.DTE.WindowBase.<get_ProjectItem>b__2c()
   at Microsoft.VisualStudio.Shell.ThreadHelper.Invoke[TResult](Func`1 method)
   at Microsoft.VisualStudio.Platform.WindowManagement.DTE.WindowBase.get_ProjectItem()
   at NuPattern.VisualStudio.Solution.VsFileTemplate.Unfold(String name, IItemContainer parent)
   at NuPattern.VisualStudio.Solution.VsFileContentTemplate.Unfold(String name, IItemContainer parent)
   at NuPattern.VisualStudio.Solution.VsItemContainerExtensions.AddContent(IItemContainer parent, String content, String name, Boolean overwrite, Boolean openFile, Encoding encoding)
   at NuPattern.Runtime.UriProviders.TextTemplate.Unfold(String name, IItemContainer parent)
   at NuPattern.Library.Commands.GenerateModelingCodeCommand.Execute()
   at NuPattern.Library.Commands.GenerateProductCodeCommand.Execute()
   at NuPattern.Library.Automation.CommandAutomation.Execute(IDynamicBindingContext context, Boolean withAutomation)
   at NuPattern.Library.Automation.CommandAutomation.Execute()
   at NuPattern.Library.Automation.EventAutomation.ExecuteCommand()
   at NuPattern.Library.Automation.EventAutomation.<>c__DisplayClassd.<Execute>b__a()
   at NuPattern.VisualStudio.TraceSourceExtensions.DoShield(ITracer traceSource, Action action, String format, Boolean showUI, String[] args)

This is arguably an issue in VS's code, but NuPattern could catch this exception and avoid failing. From what I could see there is no way to query the window to see if it would throw when returning its ProjectItem, as the properties have values just like the window for a code editor:

        window.Caption  "Solution Explorer" string
        window.Type vsWindowTypeSolutionExplorer    EnvDTE.vsWindowType
        window.Kind "Tool"  string
        window.ProjectItem  null    EnvDTE.ProjectItem

        window.Caption  "Application1.Contracts"    string
        window.Type vsWindowTypeDocument    EnvDTE.vsWindowType
        window.Kind "Document"  string
+       window.ProjectItem  'window.ProjectItem' threw an exception of type 'System.InvalidCastException'   EnvDTE.ProjectItem {System.InvalidCastException}

        window.Caption  "EndpointConfig.cs" string
        window.Type vsWindowTypeDocument    EnvDTE.vsWindowType
        window.Kind "Document"  string
+       window.ProjectItem  COM Object  EnvDTE.ProjectItem {System.__ComObject}

A try/catch on InvalidCastException on that look should fix this.