AJAX Filteredtextbox control enables you to validate the user input by disallowing the user to enter restricted characters. You can specify the set of valid characters or invalid characters that you want to filter at the time of user interaction with input textbox controls.
Properties of FilteredTextbox Control
You can learn the use of above properties and get the C# code from the tutorial of AJAX FilteredTextbox control by following the link provided at the bottom of this sample.
Try the sample below to understand the functionality of AJAX FilteredTextbox control: