maxlength for TextBox not working

If I set the maxlength field for a textbox, and have the textmode set to SingleLine, the amount of text is limited to the specified number of characters. If you change TextMode to MultiLine, the number of characters is no longer constrained. Is there any way around this?

You need javascript or RegularExpressionValidator.
Do a Google search.

ya this is right you should help of java script for do this