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

txtUserName.Clear();

This code clears the textbox. It will set the Textbox value to ""

txtUserName.Text = string.Empty;

Doesn't create object. This executes faster than txtUserName.Text = "";

txtUserName.Text = "";

Creates object and affects the performance.