Assembly: System.Web (in System.Web.dll)
The event is raised by the OnWebPartsConnecting method, and it signals that the connection process has begun (for example, a user has selected a control and clicked a connect verb), but is not yet completed. The event provides an opportunity to cancel a connection before it is complete. If the connection is successfully completed, this event is followed by the WebPartsConnected event.
Page developers can add a custom handler for the event by adding the OnWebPartsConnecting attribute to the <asp:webpartmanager> element, and assigning a custom method name to the attribute.