Arguably, your best option is to use a refactoring tool (like Resharper) to help you automate the conversion from the old name to the new name. However, if this is untenable to you for some reason, here are some alternatives:
If the types are in different assemblies you may be able to use a Type Forwarder. These allow you to redirect all references for a given type to an assembly ... but if IIRC, they can also redirect them to a new name as well.
Otherwise, within a single .cs source file you can apply a using statement:
using OldClassName = SomeNameSpace.NewClassName
This doesn't solve the problem globally, however, as it may become painful to change many .cs files to include this using statement.
Another alternative, may be to create a sub-class of the new type and name it the old name:
public class OldClassName : NewClassName
This gives you aliasing for the new class, but will require that you create duplicate public constructors and proxy static method calls to the renamed type. This is far from ideal ... and I generally don't recommend this.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…