restricting min no of characters in asp.net text box

restricting min no of characters in asp.net text box

Just use a Regular Expression Validator.

Toggle the validator's Enabled property to true or false based on the DropDownList's SelectedValue property. You can do that through a simple subroutine / function.

How you define a "character" is the question.

If you mean letters and numbers only, your ValidationExpression for the control would be: \w{2,}

If you mean only letters, your expression would be: [a-zA-Z]{2,}

If you mean only numbers, your expression would be: [0-9]{2,}

If you mean anything except white space or control characters, your expression would be: \S{2,}