.NET Framework 3.5 installation in Server 2008R2 when needed

If you want to install .NET Framework 3.5 into your Server 2008R2,than you have to take help of role management tool.This can be seen in Server Manager. In Server Manager,expand Features and click on Add Feature which can be seen in the right most corner and in that check .NET Framework 3.5.1 feature and you are done. For reference please see the screenshot below..