One nice tidbit is how to create new short type names without having to specify the full name of every non-primitive type, especially inside of generic type names.

Normally, using “using” to create a new type name, even in the presence of the appropriate namespace import, one has to fully qualify every type name that is not a keyword.

using System.Collections.Generic;
using T = System.Collections.Generic.List<string>

However, if the “using” is inside a namespace, then it will utilize any imports located in an outer namespace.

using System.Collections.Generic;
 
namespace MyCompany
{
    using T = List<string>;
}