How the hell does that Mid function even work? ReSharper shows me that it is a static function returning a String in the Microsoft.VisualBasic.Strings class, but I can't see any way of implementing that syntax in .NET.

Whatever the Mid function returns isn't used because your "abcd" string is assigned to the result immediately.
Also, I don't see how the Mid function can use your "abcd" string, since it would have to run before the " = "abcd"" part would be executed, hence it would have no knowledge of that string yet.

I suppose it doesn't something special just like CInt and the If() operator, etc. That's all the more reason for me not to use it.