Access Host object from T4 class

Question

When I try to access the Host object from a non-static method declared in <#+#> brackets, everything works ok. But I need to access it from a class method, like this:

<#+
public class ProjectTraverser
{
    public void Traverse()
    {
        var a = Host;
    }
}
#>

I get the following error when this template executes: "Compiling transformation: Cannot access a non-static member of outer type 'Microsoft.VisualStudio.TextTemplating7D03DF372FEAC3D3A28C011A41F02403.GeneratedTextTransformation' via nested type 'Microsoft.VisualStudio.TextTemplating7D03DF372FEAC3D3A28C011A41F02403.GeneratedTextTransformation.ProjectTraverser' d:\Projects\Test Solutions\GettingStarted\TelerikMvc3RazorApplication\TextTemplate2.tt"

Please share any ideas.

It is exactly like it says (can't access non-static member of outer type) but you could pass Host in a constructor to ProjectTraverser. — Just another metaprogrammer, May 02 '12 at 20:50
Thanks for your comment FuleSnabel. Not the best level of encapsulation, but nevertheless it is a solution. — Narek Malkhasyan, May 17 '12 at 11:24

GarethJ · Accepted Answer · 2012-05-18T07:01:07.153

6

As FuleSnabel commented, the declaration you're making is for a nested type, which doesn't have access to the instance variable in the enclosing type that represents the template.

What you'll want to do is add a Host property of type ITextTemplatingEngineHost to the ProjectTraverser class (probably static) and then set it from the main template.

In retrospect, I wish I'd made the main Host property static, as it's not really sensible to imagine multiple hosts for different instances of the same template in the same AppDomain, but you live and learn.

Here's a rough example:

<#@ template hostspecific="true' #>
<#
    ProjectTraverser.Host = Host;
#>
<#+ 
public class ProjectTraverser 
{
    public static ITextTemplatingEngineHost Host { get; set; }

    public void Traverse() 
    { 
        var a = Host; 
    } 
} 
#>

edited May 18 '12 at 07:01

answered May 17 '12 at 00:28

GarethJ

6,496
32
42

Thanks for your answer Gareth, could you please elaborate on "and then set it from the main template" part. As far as I understand, I must have a separate initialization method for my class, which should be called before using the class, which is pretty inconvenient. Am I right, or this could be achieved in a better way? – Narek Malkhasyan May 17 '12 at 10:11
Edited to include a small example. – GarethJ May 18 '12 at 06:58

Access Host object from T4 class

1 Answers1