What .NET Framework and C# version should I target with my class library?

Question

I\'m building a DLL class library - I want to make it usable by as many people as possible. Which version of the .NET Framework and which C# version should I use? Is it po

Answer 1

This solution works quite well. I just set up two different projects each with a unique "Project Properties->Build->Conditional compilation Symbols" and used in the code like this:

#if NET_4
            xmlReaderSettings.DtdProcessing = DtdProcessing.Ignore; 
#endif
#if NET_3_5
            xmlReaderSettings.ProhibitDtd = false;                
#endif