为什么我不能在T4模板中的类成员中访问实用程序方法？

Question

I'm trying to write a class in a T4 template that uses the Text Template Utility Methods (like WriteLine, PushIndent, PopIndent). However, if I try to call these methods in my class, I'll get a compiler error stating

Compiling transformation: Cannot access a non-static member of outer type 'Microsoft.VisualStudio.TextTemplating.TextTransformation' via nested type 'Microsoft.VisualStudio.TextTemplatingBF13B4A5FBA992E5EF81A8A7A4EACCAC3F7698E169D0F7825ED4F22A28C7C52C2B766D83F4C5ACA13E0DE0B3152B6D966E34EB8C5FC677E145F55BE0485406EC.GeneratedTextTransformation.ClassGenerator'

A MCVE (minimal complete verifiable example) would look like this:

<#+
public void FunctionSample()
{
    WriteLine("Hello"); // This works fine
}

public class SampleClass
{
    public static void StaticMethodSample()
    {
        WriteLine("Hello"); // This does not compile
    }

    public void InstanceMethodSample()
    {
        WriteLine("Hello"); // This does not compile either
    }
}
#>

Is there any way to access these utility methods within a class scope or do I have to use free functions?

(I'm running on Visual Studio 2015 Community)

Answer 1

As PetSerAl pointed out in the comments, you can just call the T4 Utility Methods in any "free function" in a Class Feature Control Block because they are inherited from the TextTransformation base class, ie these free functions are not exactly free, they are methods within the scope of an implicitly created class that derives from TextTransformation . That's why you can also access this in these functions.

So if you want to use a utility method in another class you defined in a T4 template (this class is actually a nested child class), you have to pass in a reference of TextTransformation to it, eg like this:

<#
var @object = new SampleClass(this); // Pass 'this' (TextTransformation) to the constructor
@object.SayHello();
#>

<#+
public class SampleClass // This is actually a nested child class in T4 templates
{
    private readonly TextTransformation _writer;

    public SampleClass(TextTransformation writer)
    {
        if (writer == null) throw new ArgumentNullException("writer");
        _writer = writer;
    }

    public void SayHello()
    {
        _writer.WriteLine("Hello");
    }
}
#>

More information can be found in the MSDN library .