How to Open Visual Studio 2010 Project file on Visual Studio 2008

First, you need to convert visual studio 2010 solution file (.sln) to visual studio 2008 solution file (.sln) simply follow these steps:
  1. in .sln file replace:
    1.  "Format Version 11.00" to "Format Version 10.00"
    2. "# Visual Studio 2010" to "# Visual Studio 2008"
  2. in .csproj replace
    1. "ToolsVersion=''4.0''" to "ToolsVersion=''3.5''"
    2. "Microsoft\VisualStudio\v10.0" to "Microsoft\VisualStudio\v9.0"
After that, you can Open the Solution file and work normally.
 
Note: with the WEB Project, in Web.Config file, you should remove the line "<compilation debug="true" targetFramework="4.0" />" to run on Visual Studio 2008

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