Regular Expression to accept Alphanumeric (Alphabets and Numbers) and Space in TextBox in ASP.Net

Here Mudassar Ahmed Khan has explained with an example, how to use Regular Expression (Regex) to accept/allow Alphanumeric characters i.e. Alphabets (Upper and Lower case) and Numbers (Digits) and Space in TextBox in ASP.Net using:- 1. RegularExpression Validator. 2. JavaScript. 3. jQuery.