but before 3.0 framework optional parameter is not supported http://forums.asp.net/t/1469867.aspx?Optional+parameters+in+C+3+

It will give compilation error. It is not supported in 3.5.

Optional parameter is a C# 4.0 language feature included with Visual Studio 2010 or .Net framework 4.0. So .Net framework 3.5 or older version will not allow to compile optional parameter.

Optional parameter is a C# 4.0 language feature included with Visual Studio 2010 or .Net framework 4.0. So .Net framework 3.5 or older version will not allow to compile optional parameter.

Optional parameter is nullable type if you pass the parameter value then compiler will take the value , else compiler will take defualt value and there is not .net framework dependency.