WebpartManager.ConnectWebparts Error

When executing the WebpartManager.ConnectWebparts() statement, I got the following error:

The ConnectWebParts method cannot be called after connections have already been activated (in WebPartManager.PreRender).

This problem occurred because I connected WebParts in Page_PreRender event.

     this.WebPartManager1.ConnectWebParts(provider, providerConnectionPoint,
                                          consumer, consumerConnectionPoint);

Moving it back to Page_Load event, everything works fine.