2005:
C:\Program Files (x86)\Microsoft Visual Studio 8\Common7\IDE\ItemTemplates\CSharp\1033\Class.zip
2008:
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\ItemTemplates\CSharp\Code\1033\Class.zip
2010:
C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\ItemTemplates\CSharp\Code\1033\Class.zip
Starting with Visual Studio 2012, the templates are not zipped, so you can edit each .cs template in each applicable folder directly.
2012:
C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\ItemTemplates\CSharp\Code\1033\Class\Class.cs
2013:
C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE\ItemTemplates\CSharp\Code\1033\Class\Class.cs
2015:
C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\ItemTemplates\CSharp\Code\1033\Class\Class.cs
[출처 : http://stackoverflow.com/questions/2072687/how-do-i-edit-the-visual-studio-templates-for-new-c-sharp-class-interface]