Enhancing the ThisAddin class

The ThisAddin_Startup() event is a good place to test for the correct Visio version and edition, along with checking that the Visio application events are indeed enabled; otherwise this add-in will not work properly anyway.

    private void ThisAddIn_Startup(object sender, System.EventArgs e)
    {
      try
      {
        veApplication.VisioApplication = this.Application;
        /* check prereq's */
        // check for Visio >= 2013 and Edition = PRO
        if (!this.IsVisio15ProfessionalInstalled)
        {
          MessageBox.Show(
              "This add-in requires the Professional edition of Visio",
              "Visio Professional edition required", MessageBoxButton.OK,
              MessageBoxImage.Exclamation
              );
          return;
        }
        // events must be enabled
        // -1 is TRUE, 0 is FALSE, typically anything other than 0 is TRUE
        if (!Convert.ToBoolean(Globals.ThisAddIn.Application...