Lambda Expressions in T4 Templates

Question

Whilst putting together a T4 template I threw in a simple lambda expression:

<#=string.Join(",", updateFields.ConvertAll(field => field.Name).ToArray())#>

This causes the template to fail to generate with the error:

Compiling transformation: Invalid expression term '>'   

On the line with the lambda expression.

This has been checked outside of a template and works fine. Does T4 not support working with lambda expressions? If not, are there any other language features that are unsupported in the context of a T4 template?

Thanks!

Answer 1

As a work around, you might put that code into an external class library, which you can then call from within the T4 template. I've had to do that a number of times. Its not ideal, but it works.

Answer 2

If you are using T4 in Visual Studio 2008, make sure that you have C# compiler version set to 3.5 in the template directive. It uses 2.0 by default.