Is there a performance difference between using a namespace vs explicitly calling the class from the namespace?

Question

Is there any performance benefit to explicitly calling a method directly from a namespace class library rather than using the namespace?

Here is an example of a situation I'm referring to:

// using
using System.Configuration;
public class MyClass
{
    private readonly static string DBConn = ConfigurationManager.ConnectionStrings["DBConn"].ConnectionString;
}

vs.

//explicit
public class MyClass
{
    private readonly static string DBConn = System.Configuration.ConfigurationManager.ConnectionStrings["DBConn"].ConnectionString;
}

Answer 1

No, there isn't any.

The compiler will convert all calls to a class to use the fully qualified name anyway.

This is easy enough to see in the produced IL, using any decompiler.