C# WPF Drag and Drop Button within StackPanel on a Canvas
<p>This may be a basic question but I just started using WPF and I am having troubles trying to do a simple drag and drop.</p>

<p>I created this ToolboxButton class:</p>

<pre><code>public class ToolboxButton : Button
{
    private bool _isDragging = false;
    private Point _startPoint;

    public ToolboxButton(string content)
    {
        Content = content;
        HorizontalAlignment = HorizontalAlignment.Stretch;
        Height = 30;
        Loaded += ToolboxButton_Loaded;
    }

    void ToolboxButton_Loaded(object sender, RoutedEventArgs e)
    {
        PreviewMouseLeftButtonDown += ToolboxButton_PreviewMouseLeftButtonDown;
        PreviewMouseMove += ToolboxButton_PreviewMouseMove;
    }

    void ToolboxButton_PreviewMouseMove(object sender, MouseEventArgs e)
    {
        if (e.LeftButton == MouseButtonState.Pressed &amp;&amp; !_isDragging)
        {
            Point position = e.GetPosition(null);

            if (Math.Abs(position.X - _startPoint.X) &gt; SystemParameters.MinimumHorizontalDragDistance ||
                    Math.Abs(position.Y - _startPoint.Y) &gt; SystemParameters.MinimumVerticalDragDistance)
            {
                StartDrag(e);
            }
        } 
    }

    void ToolboxButton_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        _startPoint = e.GetPosition(null);
    }

    private void StartDrag(MouseEventArgs e)
    {
        _isDragging = true;
        DataObject data = new DataObject(System.Windows.DataFormats.Text.ToString(), "abcd");
        DragDrop.DoDragDrop(e.Source as ToolboxButton, data, DragDropEffects.Move);
        _isDragging = false;
    }
}
</code></pre>

<p>This button is added in a stackpanel like so:</p>

<pre><code>ToolboxButton btnAddButton = new ToolboxButton("Button");
_toolboxView.Children.Add(btnAddButton); // _toolboxView is a stackpanel
</code></pre>

<p>And I have a Canvas with the following code:</p>

<pre><code>public class DesignerView : Canvas
{
    public DesignerView()
    {
        AllowDrop = true;
        DragOver += DesignerView_DragOver;
        Drop += DesignerView_Drop;
        PreviewDragOver += DesignerView_PreviewDragOver;
    }

    void DesignerView_PreviewDragOver(object sender, DragEventArgs e)
    {
        MessageBox.Show("previewdragover");
    }

    void DesignerView_DragOver(object sender, DragEventArgs e)
    {
        MessageBox.Show("dragover");
        if (!e.Data.GetDataPresent(typeof(ToolboxButton)))
        {
            e.Effects = DragDropEffects.None;
            e.Handled = true;
        }
    }

    void DesignerView_Drop(object sender, DragEventArgs e)
    {
        MessageBox.Show("drop");
        if (e.Data.GetDataPresent(typeof(ToolboxButton)))
        {
            ToolboxButton droppedThingie = e.Data.GetData(typeof(ToolboxButton)) as ToolboxButton;
            MessageBox.Show("You dropped: " + droppedThingie.Content);
        }
    }

    public UIElement GetView()
    {
        return this;
    }
}
</code></pre>

<p>Both Canvas and StackPanel are added in the main window like so:</p>

<pre><code>Grid contentGrid = new Grid();
Content = contentGrid;
contentGrid.Children.Add(_toolboxView.GetView());
contentGrid.Children.Add(_designerView.GetView());
</code></pre>

<p>None of the MessageBoxes ever fire and I can't find out why. The cursor changes to the "Cannot pin", a dark circle with a diagonal line inside.
Am I missing something ? I want everything to be done in the code without XML.
Maybe I have to do something on the StackPanel but I tried the code of ToolboxButton there and it didn't work either.</p>