This simple software allow you to see your XML coding structure in simple way. Beside, when you using C# coding to develop XML coding, its help you a lot. This software you can download it at http://www.microsoft.com/en-my/download/details.aspx?id=7973
Microsoft Visual Studio
From my experience right now, best compiler to do C# coding was Microsoft Visual Studio 2010. And this website will be doing c# programming base on this compiler. You can download and try it from here: http://www.microsoft.com/visualstudio/eng/downloads