Cannot see _ (underscore) in WPF content

Question

A very simple question:

Why I cant see _ (underscore) in WPF content?

For instance the content of

Answer 1

I know im late to the party but I believe that if you don't have the Label associated to a TextBox than you should use a TextBlock instead.

Changing your control to a TextBlock solves this issue since only Label has the mnemonic support