ScriptManager.SetFocus Method (String)
Sets the browser focus to the control specified by ID.
Assembly: System.Web.Extensions (in System.Web.Extensions.dll)
The SetFocus method works like the SetFocus method for the Page class. Both methods make the control with the specified ID the active control on the Web page. The SetFocus method of the ScriptManager class is used to set focus during an asynchronous postback. During postbacks and when the page is first rendered, the SetFocus method calls the SetFocus method of the Page class.
If there are multiple calls to the SetFocus method, the control in the last call receives focus.