Exception thrown when adding item to context menu after clearing bound list

[Mike]

I have a GridView that is bound to a binding list

BindingList<DataElementMap> DataElementMaps { get; set; }

mappingsGridView.DataSource = DataElementMaps;

I am adding a menu item to the Context Menu using the following

 private void mappingsGridView_ContextMenuOpening(object sender, ContextMenuOpeningEventArgs e)
{
                if (!e.ContextMenu.Items.Contains(_ceateTransformationMenuItem))
                {
                    e.ContextMenu.Items.AddRange(_ceateTransformationMenuItem);
                }
}

This works fine until I clear the data bound list.  (i.e. DataElementMaps.Clear(); ) 

After a clear is executed the above code throws the following exception
System.ArgumentException occurred
  Message=Cannot remove the specified item because it was not found in the specified Collection.
  Source=mscorlib
  StackTrace:
       at System.Collections.CollectionBase.System.Collections.IList.Remove(Object value)
       at Telerik.WinControls.RadElementCollection.CheckElementAlreadyAdded(RadElement element)
       at Telerik.WinControls.RadElementCollection.OnInsert(Int32 index, Object value)
       at System.Collections.CollectionBase.System.Collections.IList.Insert(Int32 index, Object value)
       at Telerik.WinControls.RadItemOwnerCollection.OnInsertComplete(Int32 index, Object value)
       at System.Collections.CollectionBase.System.Collections.IList.Add(Object value)
       at Telerik.WinControls.RadItemCollection.AddRange(RadItem[] value)

[Mike]

I have found the cause of this error.  I was only instatiating the menu item once  for the lifetime of the grid view control.  I change the above code to 

private void mappingsGridView_ContextMenuOpening(object sender, ContextMenuOpeningEventArgs e)
{
    if (!e.ContextMenu.Items.Contains(_ceateTransformationMenuItem))
     {
        _ceateTransformationMenuItem = new RadMenuItem("Create Transformation");
        _createTransformationMenuItem.Click += new EventHandler(CreateTransformationClick); 
        e.ContextMenu.Items.AddRange(_ceateTransformationMenuItem);               
      }
}

So it appears to me that the code that adds the menu item to the context menu items collection (CheckElementAlreadyAdded)  is looking at some other internal list to determine if the menu item exists and thus attempting to remove it from a list that from where it does not exist. 

[Dimitar]

Hi Mike,

Thank you for writing.

In this case the item is disposed when the data source is cleared and this is why you get the exception. Please note that the all context menu items are disposed at some point, however you can create new item each time or check if the item is disposed:

void radGridView1_ContextMenuOpening(object sender, Telerik.WinControls.UI.ContextMenuOpeningEventArgs e)
{
    if (!e.ContextMenu.Items.Contains(myItem))
    {
        if (myItem.IsDisposed)
        {
            myItem = new RadMenuItem("My Item");
            myItem.Click += myItem_Click;
        }
        e.ContextMenu.Items.Add(myItem);
    }
}

Please let me know if there is something else I can help you with. 

 

Regards,
Dimitar
Telerik

 

 

[Geovani]

Why not add this relevant information to the documentation? see https://docs.telerik.com/devtools/winforms/controls/gridview/context-menus/custom-context-menus . It's ridiculous that we have to spend hours googling around to find answers that should be in the documentation in the first place!.

[Dess | Tech Support Engineer, Principal]

Hi, Geovani,

I am sorry to hear that you were facing difficulties with adding items to the context menu in RadGridView. Please have in mind that we have a sample code snippet on this topic in our online documentation:

https://docs.telerik.com/devtools/winforms/controls/gridview/context-menus/modifying-the-default-context-menu#adding-menu-items-to-the-default-radgridview-context-menu 

I hope this helps.