In this lesson, we explain how Namespaces allow us to disambiguate classes that may share the same name. And we explain how the .NET Framework Class Library is so large that including all its classes in every application you write is a waste of system resources. Certain project templates include references to the typical assemblies required by a given type of application, and we demonstrate this by referencing a custom assembly of Bob's own design.
static void Main(string args)
//System.IO.StreamReader myStreamReader = new System.IO.StreamReader();
//StreamReader myStreamReader = new StreamReader();
Bob bob = new Bob();
string html = bob.Lookup("http://www.learnvisualstudio.net");
Source : MS Virtual Academy