MutuallyExclusiveCheckBox is an ASP.NET AJAX extender that can be attached to any ASP.NET CheckBox control. By adding a number of checkboxes to the same Key, only one check box with the specified key can be checked at a time. This extender is useful when a number of choices are available but only one can be chosen, similar to a radio button. The use of checkboxes however allows you to choose to uncheck a value, which is not possible normally with radio buttons. This also provides a more consistent and expected interface than using JavaScript to allow de-selection of a RadioButton item.