Ajax extender
[TargetControlType(typeof(TextBox))]
public class DisabledButtonExtender : ExtenderControlBase
{
[ExtenderControlProperty]
[DefaultValue(“”)]
[IDReferenceProperty(typeof(Button))]
Create an extender that extends a textbox and assigns to a button;
Using wich combination?

A.
[TargetControlType(typeof(TextBox))]
[IDReferenceProperty(typeof(Button))]

Explanation:
[TargetControlType(typeof(TextBox))]
public class DisabledButtonExtender : ExtenderControlBase
{
[ExtenderControlProperty]
[DefaultValue(“”)]
[IDReferenceProperty(typeof(Button))]
http://www.asp.net/web-forms/tutorials/ajax-control-toolkit/getting-started/creating-a-customajax- control-toolkitcontrol-extender-cs