Apart from what was mentioned in Solution 1, there is significantly no (or very less) difference in performance for this change as well. Because, one way or the other, compiler takes care of "
when" and "
how" after compilation,
because of optimization. The concept of namespace span back to the days of C++, where the namespaces in C were quite "complex", and you would have a namespace of struct, or union etc. C++ introduced the namespaces, that can be created on demand. C# uses the same concept, and allows you to map the types to a particular namespace, or find the objects within.
Likewise, in C#, the types are first checked up locally, and then any namespaces are checked to include the type. So, a namespace within the namespace (or class) would only mean that this package reference is only available
within the scope of the class. The other classes, or namespaces within the same file do not reference it, and thus they would use the types provided by programmer;
see the example on the SO thread that Solution 1 provided.
Scott Hanselman explained this pretty much neatly in his blog post,
Back to Basics - Do namespace using directives affect Assembly Loading? - Scott Hanselman[
^]