Excel VSTO Addin showing/hiding taskpane

I do the tutorial here. Everything works fine with a blank excel page https://msdn.microsoft.com/en-us/library/bb608590(v=vs.120).aspx When I load up a excel sheet someone gave me and go to click the toggleButton1 to show the pane I get {"The taskpane has been deleted or is otherwise no longer valid."} on the line ``` private void toggleButton1_Click(object sender, RibbonControlEventArgs e) { Globals.ThisAddIn.TaskPane.Visible = ((RibbonToggleButton)sender).Checked; } ``` Is a pointer to that task pane somehow going away? ``` Microsoft.Office.Tools.CustomTaskPane PartPhotoTaskPane; Globals.ThisAddIn.Application.WindowActivate += Application_WindowActivate; void Application_WindowActivate(Excel.Workbook Wb, Excel.Window Wn) { if (PartPhotoTaskPane != null) { PartPhotoTaskPane.Dispose(); InitalizePartPhotoViewerTaskPane(EPPF); } else { InitalizePartPhotoViewerTaskPane(EPPF); } } /// <summary> /// Start up the part photo viewer task pane /// </summary> private void InitalizePartPhotoViewerTaskPane(ExcelPartPhotoFunctions _EPPF) { //intialize the part search try { PartPhotoTaskPane = Globals.ThisAddIn.CustomTaskPanes.Add(new PartPhotoSearchPane(_EPPF), "Part Information", Globals.ThisAddIn.Application.ActiveWindow); PartPhotoTaskPane.Visible = Properties.Settings.Default.InfoPaneOpenStatus; PartPhotoTaskPane.Width = 260; } catch (Exception e) { MessageBox.Show("Error starting Part Info Toolbar:" + Environment.NewLine + e.Message + Environment.NewLine + e.StackTrace, "Error!", MessageBoxButtons.OK, MessageBoxIcon.Error); } } ``` ATTEMPT 1: Still error on the click event. I am guessing it is something related to me needing to share that pane between classes? ``` private void toggleButton1_Click(object sender, RibbonControlEventArgs e) { Globals.ThisAddIn.TaskPane.Visible = ((RibbonToggleButton)sender).Checked; } private void ExcelEvents_WorkbookActivate(Excel.Workbook wb) { var taskPane = (customTaskPanes.Where(kvp => kvp.Key.Target == wb).Select(kvp => kvp.Value).FirstOrDefault()); if (taskPane == null) { UcCenlarInvest control = new UcCenlarInvest(); taskPane = this.CustomTaskPanes.Add(control, "My pane for workbook " + wb.Name); customTaskPanes[new WeakReference(wb)] = taskPane; } } ``` ATTEMPT 2: So now the Ribbon class can get the TaskPane yet I Still get the same error. Added this : ``` private CustomTaskPane taskPane; public CustomTaskPane TaskPane { get { //return (customTaskPanes.Where(kvp => kvp.Key.Target == wb).Select(kvp => kvp.Value).FirstOrDefault()); return pane; } set { taskPane = value; } } ``` ..... ``` TaskPane = (customTaskPanes.Where(kvp => kvp.Key.Target == wb).Select(kvp => kvp.Value).FirstOrDefault()); ```