Setting a breakpoint in a T4 template

Set the following:

<#@ template debug="true" hostSpecific="true" #>
<#@ import namespace="System.Diagnostics" #>

Then in your template

Debugger.Launch();

VS will kick off the JIT debugger in a new instance of VS 2010

OK- figured it out. Launching a new instance is not an option, regardless of what Oleg's article says. (No diss to Mr. Sych, his blog is gospel for T4 code generation!)

1. Start a second instance of Visual Studio,
2. Open a file (any file) so the Debug menu shows up.
3. Select "Attach to Process..." and select the other VS.NET instance
4. Save your template in the attached instance of VS.NET (or right-click and select Run Custom Tool)

Voila.

In Visual Studio 2013:

1. Set a breakpoint in the .tt file
2. Right-click the .tt file in the solution explorer
3. Select "Debug T4 Template"
4. Done!

No attaching a second instance of Visual Studio needed.

Make sure that you turn on the debug option in the template directive:

<#@ template language="C#" debug="true" #>

This makes T4 save the source code and symbol files necessary for debugging in Visual Studio.