Question

I’m writing a custom ItemsControl (a tabbed document container), where each item (tab) can remove itself from the UI when the user closes it. However, I can’t remove it directly from the ItemsControl.Items collection, because the items can be databound. So I have to remove it from the ItemsSource, which can be anything (ICollection, DataTable, DataSourceProvider…).

In the context of my application, I know what the actual type of the ItemsSource will be, but I want that control to be more generic so that I can reuse it later.

So I’m looking for a way to remove an item from a data source, without knowing its type. I could use reflection, but it feels dirty… So far the best solution I came up with is using dynamic :

    internal void CloseTab(TabDocumentContainerItem tabDocumentContainerItem)
    {
        // TODO prompt user for confirmation (CancelEventHandler ?)

        var item = ItemContainerGenerator.ItemFromContainer(tabDocumentContainerItem);

        // TODO find a better way...
        try
        {
            dynamic items = ItemsSource;
            dynamic it = item;
            items.Remove(it);
        }
        catch(RuntimeBinderException ex)
        {
            Trace.TraceError("Oops... " + ex.ToString());
        }
    }

But I’m not really happy with it, I’m sure there must be a better way. Any suggestions would be appreciated !

Answer 1

OK, I found a solution…

• If the ItemsSource is databound, I either raise an event (for use with code-behind) or invoke a command (for use with a ViewModel) to remove the item from the ItemsSource collection.

• If it’s not databound, I raise an event to prompt the user for confirmation, and I remove the container directly from Items

  public static readonly DependencyProperty CloseTabCommandProperty =
      DependencyProperty.Register(
          "CloseTabCommand",
          typeof(ICommand),
          typeof(TabDocumentContainer),
          new UIPropertyMetadata(null));
  
  public ICommand CloseTabCommand
  {
      get { return (ICommand)GetValue(CloseTabCommandProperty); }
      set { SetValue(CloseTabCommandProperty, value); }
  }
  
  public event EventHandler<RequestCloseTabEventArgs> RequestCloseTab;
  public event EventHandler<TabClosingEventArgs> TabClosing;
  
  internal void CloseTab(TabDocumentContainerItem tabDocumentContainerItem)
  {
      if (ItemsSource != null) // Databound
      {
          object item = ItemContainerGenerator.ItemFromContainer(tabDocumentContainerItem);
          if (item == null || item == DependencyProperty.UnsetValue)
          {
              return;
          }
          if (RequestCloseTab != null)
          {
              var args = new RequestCloseTabEventArgs(item);
              RequestCloseTab(this, args);
          }
          else if (CloseTabCommand != null)
          {
              if (CloseTabCommand.CanExecute(item))
              {
                  CloseTabCommand.Execute(item);
              }
          }
      }
      else // Not databound
      {
          if (TabClosing != null)
          {
              var args = new TabClosingEventArgs(tabDocumentContainerItem);
              TabClosing(this, args);
              if (args.Cancel)
                  return;
          }
          Items.Remove(tabDocumentContainerItem);
      }
  }