VSTO: which event cannot hooked to the object directly?

Question

For some event, the subscription by hooking the event directly object is failing but working when you use a local variable. I haven't figured out why yet, who does?

I came across this mystery as I start working with CommandBarsEvents.OnUpdate, in order to detect interaction with a shape, what can comes with certain problems as described here. There are other events with that problem?

score 0 · Answer 1 · answered Jun 09 '16 at 07:54

to keep clear here comes an (incomplete) overview of events which are affected and which not

events what DO need a local variable

this.Application.CommandBars.OnUpdate
.

Their code has to be like this:

using Office = Microsoft.Office.Core;
namespace Project
{
    public partial class AddIn
    {      
        private Office.CommandBars commandBars; //declaration of local variable

        private void ThisAddIn_Startup(object sender, System.EventArgs e)
        {
            commandBars = this.Application.CommandBars; //initialization of local variable
            commandBars.OnUpdate += new Office._CommandBarsEvents_OnUpdateEventHandler(commandBars_OnUpdate); //"indirect" subscription to event`
        }

    }
}

events what NOT need a local variable

((InteropExcel.AppEvents_Event)Application).NewWorkbook
this.Application.WorkbookNewSheet
this.Application.WorkbookOpen
.

Their code can be like this:

using Office = Microsoft.Office.Core;
namespace Project
{
    public partial class AddIn
    {      
        private void ThisAddIn_Startup(object sender, System.EventArgs e)
        {
             ((InteropExcel.AppEvents_Event)Application).NewWorkbook += new InteropExcel.AppEvents_NewWorkbookEventHandler(Excel_NewWorkbook_EventHandler); //"direct" subscription to event`
        }

    }
}

VSTO: which event cannot hooked to the object directly?

1 Answers1