Validate Textbox

Question

Hello Validate text box that accept only Digits Letters and First charecter should be Capital P only and the Maximum length of Textbox should be 6 charecters. i know the code to accept digits and letters and Max length but i don't know how to set First charecter of Text box to capital P. pls some one provide me code .. Thanks

Vulpes · Answer

The easiest way is to use a regular expression: using System.Text.RegularExpressions; // .... string regExp = ^P[a-zA-Z0-9]{5}$; if (!Regex.IsMatch(textBox1.Text regExp)) { MessageBox.Show(Invalid input. Please amend); textBox1.Focus(); return; } The above assumes the text will be exactly 6 characters long. If it could be between 2 and 6 characters then use instead: string regExp = ^P[a-zA-Z0-9]{15}$;