Want to get free Open Source Softwares in C#. You can find some of the projects here
AspectDNG - AspectDNG is a .NET multi-language aspect weaver. Aspects and base code may be written in any programming language, as soon as it compiles into MSIL.
Spring.net - Spring.NET is a port of the Java based Spring Framework. Spring for Java contains a lot of functionality and features, many more than Spring.NET currently offers. The initial release of Spring.NET contains a full featured Inversion of Control container.
SAX.NET - SAX dot NET is a C# port of the original Java based SAX API specifications.