如可检测.NET Framework是否安装及安装版本

.Net Framework 2.0

http://blogs.msdn.com/b/astebner/archive/2008/11/11/9061169.aspx

.Net Framework 3.0

https://msdn.microsoft.com/en-us/library/aa480173.aspx

.Net Framework 3.5 

https://msdn.microsoft.com/library/cc160716.aspx

.Net Framework 4

https://msdn.microsoft.com/en-us/library/vstudio/ee942965(v=vs.100).aspx

.Net Framework 4.5 and 4.6

https://msdn.microsoft.com/en-us/library/ee942965(v=vs.110).aspx

判断.Net Framwork的安装版本

https://msdn.microsoft.com/en-us/library/hh925568(v=vs.110).aspx