What is the difference between these three ways to clear a Textbox?

Question

I am bit confused between the below three ways to clear the contents of a textbox. I am working with WPF and found All are working, but I am unable to find the difference.

Answer 1

"" creates an object while String.Empty creates no object. So it is more efficient to use String.Empty.

Refference: String.Empty vs ""

Regarding .Clear() i didnot get better answer then @syned's answer.