The ClientSideEvents object contains string properties that allow client-side JavaScript function names to be specified for handling a variety of events that occur on the client. The JavaScript function with the same name must then be defined somewhere within the page in order for the event to be fired.
The JavaScript can be written directly into the aspx page or it can be added in the code-behind file using the Page.RegisterClientScriptBlock function.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2