Eclipse is an IDE, not a "Framework". Juno is a version release of Eclipse (specifically, version 4.2, note that we're now up to Kepler which is 4.3).
Eclipse is not a C#/.NET IDE, it's primarily a Java and C/C++ IDE.
You can add C# support to Eclipse through a third-party plugin: http://emonic.sourceforge.net/ but I can't find any information regarding the efficacy of this plugin.
If you want a good C# IDE, install Visual C# Express: http://www.microsoft.com/visualstudio/eng/products/visual-studio-express-products
If you don't want to use Visual Studio, then use MonoDevelop: http://monodevelop.com/
