How to Focus an TextBox on Button click

Question

So how to Focus an TextBox on Button click using the MVVM Pattern?

i created an simple Testproject Based on this Answer which works on the first click, but after tha

Answer 1

I got the same issue before. I did a trick. In your OnClick method, do something like this:

if(IsFocus == true)
   IsFocus = false;
IsFocus = true;