VSTO MS Project 2007 Add-In Button Events Stop firing after a few minutes

Question

I'm writing an MS Project 2007 Add-in (VS 2010, WinXP) that creates a toolbar w/button and assigns a HelloWorld onclick eventhandler to said button.

The problem

After being installed, the plugin creates the button, wires up the click event, and everything works just fine. However, after a few minutes, the onclick event inexplicably stop firing.

Everything I've read says that I need to define my toolbar/button in the global scope, which I've done. However, the onclick event still gets unhooked after a few minutes of runtime.

One other weird symptom I'm experiencing is that when I toggle it in the COM Add-ins Dialog box (after its stopped working), I get this weird message:

"com object that has been seperated from its underlying RCW cannot be used"

...which is strange, because in this simple application, I'm not releasing any COM objects.

Any suggestions?

---

The Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
using MSProject = Microsoft.Office.Interop.MSProject;
using Office = Microsoft.Office.Core;



namespace Test_Project2007_Addin
{
    public partial class ThisAddIn
    {
        private Office.CommandBar cmdBar;   // Hello World Toolbar
        private Office.CommandBarButton cmdBtn01; // Hellow World Button

        private string cmdBarName   = "Hello World Toolbar";
        private string cmdBtn01Name = "HelloWorld";

    
        private void ThisAddIn_Startup( object sender, System.EventArgs e ) {

            // Define the toolbar

            cmdBar = this.Application.CommandBars.Add( 
               cmdBarName, Office.MsoBarPosition.msoBarTop, false, true );
            cmdBar.Visible           = true;
            
            // Define the button
            
            cmdBtn01                 = cmdBar.Controls.Add( Office.MsoControlType.msoControlButton, missing, missing, missing, true ) as Office.CommandBarButton;
            cmdBtn01.FaceId          = 422;
            cmdBtn01.Caption         = "Hello World";
            cmdBtn01.Tag             = cmdBtn01Name;
            cmdBtn01.DescriptionText = "Hello World";
            cmdBtn01.TooltipText     = "Hello World";
            cmdBtn01.Click          += new Microsoft.Office.Core._CommandBarButtonEvents_ClickEventHandler( HelloWorld );

        }

        private void ThisAddIn_Shutdown( object sender, System.EventArgs e ) {

        }

        private void HelloWorld( Microsoft.Office.Core.CommandBarButton barButton, ref bool someBool ) {
            System.Windows.Forms.MessageBox.Show( "Hello, World!" );
        }



        #region VSTO generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InternalStartup()
        {
            this.Startup += new System.EventHandler(ThisAddIn_Startup);
            this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown);
        }
        
        #endregion
    }
}

Answer 1

Try adding the CommandBars as a private member variable. Maybe CommandBars is getting garbage collected. See if this fixes your RCW issue - if not it may be another plugin.

If this doesn't work, maybe try making Application a local member. Sorry - I don't have MS Project to test this out.

private CommandBars cmdBars; // app command bars

private void ThisAddIn_Startup( object sender, System.EventArgs e ) {
  //..
  cmdBars = this.Application.CommandBars;
  cmdBar = cmdBars.Add(cmdBarName, Office.MsoBarPosition.msoBarTop, false, true );
  //..
}