Here's I wrote some code to validate user input without using if\else statements.
I believe in scalability is the most important aspect in our problems solution. Let's say we are required to permit only numerics in some text boxes; we shouldn't develop something like that
if(((e.KeyChar < '0' || e.KeyChar >'9')) we HAVE to use Regular Expression Regex class and match string with pattern (when something changes go and change patterns) you can set it in App.Config file which means you won't open the source code again.
Common Regular Expression Patterns