title: In the end of typing, I want to check how many time user press key "Backspace"
body: <p>I want to make program with C# that can to know how many times user using key "backspace". This is the scenario, User will typing in richtextbox, after they finished typing, I want to know from begining until they press enter, how many time they used "backspace". That information will show up in messagebox like "Backspace used 10 time". Please help me</p>