https://msdn.microsoft.com/en-us/library/ff477603(v=vs.100).aspx
This topic provides an overview of the .ttinclude file that contains utility classes that help the ADO.NET templates with the code generation process. This file is used by the ADO.NET EntityObject Generator Template and ADO.NET Self-Tracking Entity Generator Template templates. You should not modify the .ttinclude file. However, you can use the helper functions that are defined in this file in your own templates.
The Visual Basic and C# versions of the .ttinclude file are installed with Microsoft Visual Studio 2010, in the <Visual Studio installation path>Common7IDEExtensionsMicrosoftEntity Framework ToolsTemplatesIncludes directory.
Use the Include directive to include the file in other text templates. When you add the Include directive to a text template, the system merges the public APIs of the included file with the code in the text template. The Include directive accepts a file name with the full path, or only the name of the included file. If you only specify the name, the text template transformation engine will search well known locations to find the file. For more information, see How to: Include Files in Text Templates. In the following example only the name of the .ttinclude file is specified: