Unable to cast object of type 'System.Windows.Controls.Grid' to type 'System.Windows.Shapes.Ellipse'?
<p>I'm implementing a drag and drop wpf application and i have created 3 ellipse, i'm using thumb control to drag and drop the ellipse in the map, and i wish to get the drop position for ellipse. However i get an error when drag ellipse as below:</p>

<blockquote>
  <p>Unable to cast object of type 'System.Windows.Controls.Grid' to type
  'System.Windows.Shapes.Ellipse'</p>
</blockquote>

<p>My XAML:</p>

<pre><code> &lt;Window x:Class="DragandDropMFP.MainWindow"
                xmlns:local="clr-namespace:DragandDropMFP"
                xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
                Title="MainWindow" Height="350" Width="525"&gt;

    &lt;Grid x:Name="maingrid" MouseMove="MainGrid_MouseMove"&gt;
        &lt;Grid.Background&gt;
            &lt;ImageBrush ImageSource="/Map/Capture.Png" /&gt;
        &lt;/Grid.Background&gt;


        &lt;Canvas&gt;
            &lt;Thumb Canvas.Left="38" Canvas.Top="22" DragDelta="Thumb_DragDelta"&gt;
                &lt;Thumb.Template&gt;
                    &lt;ControlTemplate&gt;
                        &lt;Viewbox Width="50" Height="50"&gt;
                            &lt;Grid Width="20" Height="20"&gt;
                                &lt;Ellipse 
                                 Fill="Blue"
                                 MouseMove="DragMouseMove"/&gt;
                                &lt;TextBlock HorizontalAlignment="Center" Text="Printer1" FontSize="4" TextAlignment="Center" VerticalAlignment="Center"/&gt;
                            &lt;/Grid&gt;
                        &lt;/Viewbox&gt;
                    &lt;/ControlTemplate&gt;
                &lt;/Thumb.Template&gt;
            &lt;/Thumb&gt;


            &lt;Thumb Canvas.Left="37" Canvas.Top="100" DragDelta="Thumb_DragDelta"&gt;
                &lt;Thumb.Template&gt;
                    &lt;ControlTemplate&gt;
                        &lt;Viewbox Width="50" Height="50"&gt;
                            &lt;Grid Width="20" Height="20"&gt;
                                &lt;Ellipse Fill="Yellow"
                                 MouseMove="DragMouseMove"/&gt;
                                &lt;TextBlock HorizontalAlignment="Center" Text="Printer2" FontSize="4" TextAlignment="Center" VerticalAlignment="Center"/&gt;
                            &lt;/Grid&gt;
                        &lt;/Viewbox&gt;
                    &lt;/ControlTemplate&gt;
                &lt;/Thumb.Template&gt;
            &lt;/Thumb&gt;


            &lt;Thumb Canvas.Left="37" Canvas.Top="174" DragDelta="Thumb_DragDelta"&gt;
                &lt;Thumb.Template&gt;
                    &lt;ControlTemplate&gt;
                        &lt;Viewbox Width="50" Height="50"&gt;
                            &lt;Grid Width="20" Height="20"&gt;
                                &lt;Ellipse Fill="Red"
                                 MouseMove="DragMouseMove"/&gt;
                                &lt;TextBlock HorizontalAlignment="Center" Text="Printer3" FontSize="4" TextAlignment="Center" VerticalAlignment="Center"/&gt;
                            &lt;/Grid&gt;
                        &lt;/Viewbox&gt;
                    &lt;/ControlTemplate&gt;
                &lt;/Thumb.Template&gt;
            &lt;/Thumb&gt;
        &lt;/Canvas&gt;

        &lt;TextBlock x:Name="ctlStatus" HorizontalAlignment="Stretch" Height="30" TextWrapping="Wrap" Text="status" VerticalAlignment="Bottom" RenderTransformOrigin="0.495,-4.7" /&gt;

    &lt;/Grid&gt;
&lt;/Window&gt;
</code></pre>

<p>My xaml.cs :</p>

<pre><code>  public MainWindow()
        {
            InitializeComponent();
        }

       private void MainGrid_MouseMove(object sender, MouseEventArgs e)
        {
            Mouse.OverrideCursor = Cursors.Arrow;
            objmoveposition(sender, e);
        }

        private void DragMouseMove(object sender, MouseEventArgs e)
        {

            Mouse.OverrideCursor = Cursors.Hand;
            objmoveposition(sender, e);
        }

        private void objmoveposition(object sender, MouseEventArgs e)
        {

            if (e.LeftButton == MouseButtonState.Pressed)
            {
                if (Mouse.OverrideCursor == Cursors.Hand)
                {
                    Ellipse objTextbox = (Ellipse)sender; &lt;--Error

                if (objTextbox != null)
                    {
                    //----&lt; Move Control &gt;---- 
                    Point mousePoint = e.GetPosition(this);

                    //&lt; Vertical &gt; 
                    int posY = (int)mousePoint.Y;
                    int actHeight = (int)Application.Current.MainWindow.Height;
                    int margin_Bottom = actHeight - (posY + (int)objTextbox.Height + (int)SystemParameters.CaptionHeight + (int)SystemParameters.BorderWidth + 4);


                    //&lt; Horizontal &gt; 
                    int posX = (int)mousePoint.X;
                    int actWidth = (int)Application.Current.MainWindow.Width;
                    int margin_Right = actWidth - (posX + (int)objTextbox.Width + (int)SystemParameters.BorderWidth);


                    ctlStatus.Text = "Top=" + posY + " margin_bottom=" + margin_Bottom + " WinHeigth=" + actHeight + Environment.NewLine + " Left=" + posX + " margin_Right=" + margin_Right + "WinWidth=" + actWidth;
                    //ctlStatus.Text = "position=" + objTextbox.ActualHeight;
                }
             }

            }


        }


        private void Thumb_DragDelta(object sender, System.Windows.Controls.Primitives.DragDeltaEventArgs e)
        {
            UIElement thumb = e.Source as UIElement;

            Canvas.SetLeft(thumb, Canvas.GetLeft(thumb) + e.HorizontalChange);
            Canvas.SetTop(thumb, Canvas.GetTop(thumb) + e.VerticalChange);
        }
</code></pre>

<p>Output:
<a href="https://i.stack.imgur.com/RQaDF.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RQaDF.jpg" alt="enter image description here"></a></p>

<p>Your guidance is highly appreciated!
Thanks!</p>