how to validate text box

add this event to textbox

this.txtBox.Validating += new System.ComponentModel.CancelEventHandler(this.numberBox_Validating);

use this function to validate

    private void numberBox_Validating(object sender, CancelEventArgs e)     {         try         {             int numberEntered = int.Parse(numberBox.Text);             if (numberEntered < 1 || numberEntered > 10)             {                 e.Cancel = true;                 MessageBox.Show("You have to enter a number between 1 and 10");             }         }         catch (FormatException)         {             e.Cancel = true;             MessageBox.Show("You need to enter an integer");         }     }

the above code validates numbers, u can use ascii value to check for your range of specail characters