Question

I have a WPF application where I need to do something like that :

<ItemsControl x:Name="lstProducts">
   <ItemsControl.ItemTemplate>
      <DataTemplate>
         <TextBlock Text="{Binding ProductName}" />
      </DataTemplate>
   </ItemsControl.ItemTemplate>
</ItemsControl>

I set the ItemsSource in code like this : lstProducts.ItemsSource = MyEFContext.Products;

Up to now everything is working fine. Now I want to use my own UserControl to display a product instead of the TextBlock like that.

<ItemsControl x:Name="lstProducts">
   <ItemsControl.ItemTemplate>
      <DataTemplate>
         <my:ProductItemCtl ProductName="{Binding ProductName}" />
      </DataTemplate>
   </ItemsControl.ItemTemplate>
</ItemsControl>

In my userControl, I created a DependencyProperty like that (see below) where I set the ProductName in the OnProductNameChanged callback.

The TextBlock in my usercontrol is not updated when binding the ItemsControl, and the callback is not launched.

#region ProductName

        /// <summary>
        /// ProductName Dependency Property
        /// </summary>
        public static readonly DependencyProperty ProductNameProperty =
            DependencyProperty.Register("ProductName", typeof(String), typeof(ProductItemCtl),
                new FrameworkPropertyMetadata("",
                    new PropertyChangedCallback(OnProductNameChanged)));

        /// <summary>
        /// Gets or sets the ProductName property. This dependency property 
        /// indicates ....
        /// </summary>
        public String ProductName
        {
            get { return (String)GetValue(ProductNameProperty); }
            set {  SetValue(ProductNameProperty, value); }
        }

        /// <summary>
        /// Handles changes to the ProductName property.
        /// </summary>
        private static void OnProductNameChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ProductItemCtl target = (ProductItemCtl)d;
            String oldProductName = (String)e.OldValue;
            String newProductName = target.ProductName;
            target.OnProductNameChanged(oldProductName, newProductName);
        }

        /// <summary>
        /// Provides derived classes an opportunity to handle changes to the ProductName property.
        /// </summary>
        protected virtual void OnProductNameChanged(String oldProductName, String newProductName)
        {
            // Set Product Name in the display Here!
            this.txtProductName.Text = newProductName;
        }

        #endregion

Answer 1

Not an answer, but i can’t write this as comment. What happens if you simplify your code like this:

public static readonly DependencyProperty ProductNameProperty = DependencyProperty.Register(
    "ProductName", typeof(string), typeof(ProductItemCtl), 
    new FrameworkPropertyMetadata(string.Empty,
        (o, e) => ((ProductItemCtl)o).txtProductName.Text = (string)e.NewValue));