ClientScriptManager.RegisterStartupScript Method (Type, String, String)
Registers the startup script with the Page object using a type, a key, and a script literal.
Assembly: System.Web (in System.Web.dll)
A client script is uniquely identified by its key and its type. Scripts with the same key and type are considered duplicates. Only one script with a given type and key pair can be registered with the page. Attempting to register a script that is already registered does not create a duplicate of the script.
Call the IsStartupScriptRegistered method to determine whether a startup script with a given key and type pair is already registered and avoid unnecessarily attempting to add the script.
In this overload of the RegisterStartupScript method, you must make sure that the script provided in the script parameter is wrapped with a <script> element block.
The script block added by the RegisterStartupScript method executes when the page finishes loading but before the page's OnLoad event is raised. The script blocks are not guaranteed to be output in the order they are registered. If the order of the script blocks is important, use a StringBuilder object to gather the scripts together in a single string, and then register them all in a single client script block.
The following code example demonstrates the use of the RegisterStartupScript method. Note that the beginning and closing script tags are included within the script parameter. To have the script tags added based on an additional parameter setting, see the RegisterStartupScript method.