#715 – Using the Thumb Control to Drag Objects on a Canvas

You can use the Thumb control for simple dragging of objects on a Canvas.  You set the Template of the Thumb control to contain the actual element to be dragged and then handle the thumb’s DragDelta event.

Below is a Canvas containing three controls, each wrapped in a Thumb and therefore draggable.

        <Thumb Canvas.Left="10" Canvas.Top="20" Canvas.ZIndex="99"  DragDelta="Thumb_DragDelta">
                    <Image Width="60" Height="60" Source="Crown.jpg"/>
        <Thumb Canvas.Left="100" Canvas.Top="60" DragDelta="Thumb_DragDelta">
                    <Image Width="80" Height="100" Source="HenryII.jpg"/>
        <Thumb Canvas.Left="30" Canvas.Top="180" DragDelta="Thumb_DragDelta">
                    <Label Content="Westminster, 19-Dec-1154"/>

In the event handler for each of the Thumb controls, we simply adjust the thumb’s position on the Canvas.

        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);



About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

2 Responses to #715 – Using the Thumb Control to Drag Objects on a Canvas

  1. Easiest way to implement dragging that I know of in WPF.

  2. David Ngugi says:

    Awesome thank you! simplest method i’ve seen and implemented

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: