How to set the Key Char value in a text box to enter only numbers?

Question

Dear Friends,

I have a problem like this,

I need to validate the text box by allowing only for numbers. So How do you do that?

I have found the given below code, but actually I don't know which keychar is for which key. Could you plz anybody help me to validate the above mentioned text box and also if you have a chart or any reference which I can go through to understand that which keychar is for which character, that would be a great help for me.........

Thank you!