omg, whats wrong with proprieties on your textbox's?
that code is just.. jesus..
go on proprieties, find ReadOnly, and set it to True
Oh and, sharing your code on a image is quite stupid, mainly if you are just giving out the .exe to run the program, without source. Plus, you are using .net framework 4.0 and since not everyone is using it, you should have said it.
An advice if you are actually learning C#, you should rename your controls like:
Textbox: txtName or txtUse
Button: btnName or btnUse
etc...
It is way better to understand, mainly on big codes, instead of having button2.. or button1.. or just "Credits". Using just "Credits" isnt really good, because if you have a button and a textbox for credits stuff, and you name them both "Credits", there you go.. problems.
So you could just use:
btnCredits
txtCredits
Good luck on C#