WPF

public class MyCanvas : Canvas
{

    private static MyCanvas ThisCanvas;

    public MyCanvas()
    {
        ThisCanvas = this;
    }

    ...

}

Kenneth Haugland wrote:

how many instances will share this value?

private static void OnItemsSourcePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    var canvas = (MyCanvas)d;
    canvas.OnItemsSourcePropertyChanged(e);
}

protected virtual void OnItemsSourcePropertyChanged(DependencyPropertyChangedEventArgs e)
{
    repopulateChildren(this);
    
    var compositeCollection = e.OldValue As CompositeCollection;
    if (compositeCollection != null)
    {
        foreach (CollectionContainer item in compositeCollection)
        {
            var elements = (ObservableCollection<UIElement>)item.Collection;
            elements.CollectionChanged -= collectionChangedHandler;
        }
    }
    else
    {
        var elements = e.OldValue as INotifyCollectionChanged;
        if (elements != null)
        {
            elements.CollectionChanged -= collectionChangedHandler;
        }
    }

    compositeCollection = e.NewValue As CompositeCollection;
    if (compositeCollection != null)
    {
        foreach (CollectionContainer item in compositeCollection)
        {
            var elements = (ObservableCollection<UIElement>)item.Collection;
            elements.CollectionChanged += collectionChangedHandler;
        }
    }
    else
    {
        var elements = e.NewValue as INotifyCollectionChanged;
        if (elements != null)
        {
            elements.CollectionChanged += collectionChangedHandler;
        }
    }
}

private void collectionChangedHandler(object sender, NotifyCollectionChangedEventArgs e)
{
    ...
}

elements.CollectionChanged -= (sender, ee) => MyCollectionChangedHandler(cv, sender, ee);

        private static void MyCollectionChangedHandler(MyCanvas cv, object sender, NotifyCollectionChangedEventArgs e)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace MyApplication
{
    public static class TextBoxUpdateExplicitBinding
    {


        private static TextBox tb;
        private static List<TextBox> MyList;

        static TextBoxUpdateExplicitBinding()
        {
            MyList = new List<TextBox>();
        }

        #region "UpdateSourceOnKeyProperty"

        public static readonly DependencyProperty UpdateSourceOnKeyProperty =
           DependencyProperty.RegisterAttached(
               "UpdateSourceOnKey",
               typeof(Key),
               typeof(TextBoxUpdateExplicitBinding),
               new FrameworkPropertyMetadata(Key.None, KeyChanged));

        public static void SetUpdateSourceOnKey(UIElement element, Key value)
        {
            element.SetValue(UpdateSourceOnKeyProperty, value);
        }

        public static Key GetUpdateSourceOnKey(UIElement element)
        {
            return (Key)element.GetValue(UpdateSourceOnKeyProperty);
        }

        private static void KeyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
        {
            tb = (TextBox)obj;
            if (!MyList.Contains(tb))
            {
                MyList.Add(tb);
                tb.PreviewKeyDown += TextBoxKeyDown;
            }
        }
        #endregion

        static void TextBoxKeyDown(object sender, KeyEventArgs e)
        {
            tb = (TextBox)sender;
            if (tb == null) return;

            var propertyValue = (Key)tb.GetValue(UpdateSourceOnKeyProperty);
            if (e.Key != propertyValue) return;

            var bindingExpression = tb.GetBindingExpression(TextBox.TextProperty);
            if (bindingExpression != null) bindingExpression.UpdateSource();
        }

        public static DependencyProperty BindProperty = DependencyProperty
                        .RegisterAttached("Bind",
                        typeof(bool),
                        typeof(TextBoxUpdateExplicitBinding),
                        new PropertyMetadata(AttachCommand));

        public static void SetBind(DependencyObject d, bool command)
        {
            d.SetValue(BindProperty, command);
        }

        private static void AttachCommand(DependencyObject d,
            DependencyPropertyChangedEventArgs e)
        {
            (d as Button).Click += Button_Click;
        }

        private static void Button_Click(object sender, RoutedEventArgs e)
        {
            var bindingExpression = tb.GetBindingExpression(TextBox.TextProperty);
            if (bindingExpression != null) bindingExpression.UpdateSource();
        }
    }
}

<TextBox x:Name="tb" Grid.Column="0" local:TextBoxUpdateExplicitBinding.UpdateSourceOnKey="Return"
                   Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type local:SearchControl}},
                                  Path=SearchText,
                                  UpdateSourceTrigger=Explicit,
                                  Mode=OneWayToSource }"/>
          <Button  Grid.Column="1" local:TextBoxUpdateExplicitBinding.Bind="True" >
              <ContentControl>
                  <Image Source="pack://application:,,,/Icons/Search.png" Height="20" Width="20"/>
              </ContentControl>
          </Button>

Kevin Marois wrote:

How do you unit test a piece of UI becoming visible/invisible? The bound bool may be correct, but the converter could fail.

Kevin Marois wrote:

How do you unit test data validations?

Pete O'Hanlon wrote:

(this is assuming you aren't using the standard visibility converter

zahalul wrote:

Can you please send a C# code ?

     <StackPanel x:Name="grd">

        <ListView x:Name="listView">
            <ListView.View>
                <GridView>
                    <GridViewColumn Header="Severity" DisplayMemberBinding="{Binding Icon}"/>
                    <GridViewColumn Header="Id" DisplayMemberBinding="{Binding Id}"/>
                    <GridViewColumn Header="Name" DisplayMemberBinding="{Binding Name}"/>
                    <GridViewColumn Header="Immagine" >
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <Image Source="{Binding ImagePath}" />
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                </GridView>
            </ListView.View>
        </ListView>
     </StackPanel>
</Window>

public partial class MainWindow : Window
    {
        public class MyItem
        {
            public string Icon { get; set; }

            public int Id { get; set; }

            public string Name { get; set; }

            public string ImagePath { get; set; }       
        }

        public MainWindow()
        {
            InitializeComponent();

            MyItem Item = new MyItem();

            Item.Icon = "1";
            Item.Id = 0;
            Item.Name = "Zvika";
            Item.ImagePath = "icon1.png";
            this.listView.Items.Add(Item);
        }

     }