ClientScriptManager.IsStartupScriptRegistered Method (String)
Determines whether the startup script is registered with the Page object using the specified key.
Assembly: System.Web (in System.Web.dll)
Call this method before calling the RegisterStartupScript method to avoid registering duplicate scripts. This is particularly important if the script requires a large amount of server resources to create.
A startup script is uniquely identified by its key and its type. Scripts with the same key and type are considered duplicates.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.