In a T4 template the executing assembly is not yours but one from the T4 engine.

To access types from your assemblies, you have to perform the following steps:

1. Add a reference to your assembly to the template. Put that at the top of it:

   <#@ assembly name="$(SolutionDir)
         
          \bin\Debug\
          
           .dll" #>
          
         

2. Import the namespace of your assembly. Put that somewhere below the previous line:

   <#@ import namespace="
         
          .
          
           " #>
          
         

3. To access the types in this assembly, pick one of them and get the assembly from it:

   var assembly = typeof(
         
          ).Assembly;var types = assembly.GetTypes()                    .Where(t => String.Equals(                        t.Namespace,                        "RepoLib.Rts.Web.Plugins.Profiler.Models",                        StringComparison.Ordinal))                    .ToArray();