I am trying to implement the following code:

private void MyWorkspace_Startup(object sender, EventArgs e)        
this.OnWorkspaceStartup +=  new zenOn.OnWorkspaceStartupEventHandler(MyWorkspace_O nWorkspaceStartup);            
this.OnWorkspaceExit += new zenOn.OnWorkspaceExitEventHandler(MyWorkspace_OnWo rkspaceExit);            
this.OnElementDoubleClicked +=  new zenOn.OnElementDoubleClickedEventHandler(MyWorkspa ce_OnElementDoubleClicked);        

the problem is that (this.OnElementDoubleClicked) is not defined.

Could you please tell me what reference I need to add the double click event?

thanks in advance