Strange compiler behaviour - optional parameter

Question

In my project some developer added method that has optional parameter in parameters list:

public static string GeneratetPopupCall(string pageName,bool withEscapeChar = false)

I know that optional parameters are part of C# 4.0. But our project is targeted to .net 3.5. (C# 3.0)

My question is:
Why it compiles if 3.5 doesn't support optional parameters? Why that is no compilation or syntax error?

Answer 1

You are using the 4.0 compiler, targeted at the 3.5 framework.

This compiles to a runtime 2.0 compatible IL.

Answer 2

As long as you use Visual Studio 2010, you can consume optional parameters even with older .NET Frameworks then 4.0.

The more information can find here