T4 stands for Text template transformation toolkit is template based code generation engine. So you can write C# code in T4 templates ( .tt is the extension) files and those c# codes execute to generate the file as per the written C# logic.It is used in Entityfreamework, MVC to create strongly type views.

T4 is used within Microsoft in ASP.NET MVC for the creation of the views and controllers, ADO.NET Entity Framework for entity generation, and ASP.NET Dynamic Data.It is also used outside of Microsoft in projects such as Sub Sonic.T4 templating is also supported in Mono Development.

Basic this comes in EF first and MVC. T4- Text template transformation toolkit

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