Assembly: System.Web (in System.Web.dll)
The event is raised by the OnWebPartAdding method after the process of adding a control to a zone has begun. This event provides an opportunity to cancel the process before it is complete. If the adding process is successful, this event is followed by the WebPartAdded event.
Page developers can provide custom handlers for the event by adding the OnWebPartAdding attribute to the <asp:webpartmanager> element in a page, and assigning a custom method name to the attribute.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.