Use T4 Template
T4 is a general-purpose templating engine you can use to generate C# code, Visual Basic code, XML, HTML, or text of any kind. The first step in using T4 is to create a template file, which is a mix of literal text, code, and processing directives. The T4 template processor will transform this file into a text file of the desired type by executing the code and processing directives inside.
The below link helps you to develop custom template for entityframework using T4 templatehttp://msdn.microsoft.com/en-us/data/gg558520.aspx
Hope this helps