TouchFrameEventArgs.GetTouchPoints Method (IInputElement)

.NET Framework (current version)

Returns a collection that contains the current touch point for each active touch device relative to the specified element.

Namespace:   System.Windows.Input
Assembly:  PresentationCore (in PresentationCore.dll)

public TouchPointCollection GetTouchPoints(
	IInputElement relativeTo


Type: System.Windows.IInputElement

The element that defines the coordinate space. To use WPF absolute coordinates, specify relativeTo as null.

Return Value

Type: System.Windows.Input.TouchPointCollection

A collection that contains the current TouchPoint for each active TouchDevice.

The following code processes the touch points retrieved from the TouchFrameEventArgs. When a touch is pressed on the canvas, the TouchDevice is captured to the canvas. When the touch is raised, the TouchDevice is released. When a touch moves across the canvas, the Id is checked. If the Id matches the Id of the primary touch point, which indicates the first touch, its location is recorded. If the move came from the second touch, a line is drawn from the position of the first touch to the position of the second touch.

This example is part of a larger example that is available in the Touch class overview.

foreach (TouchPoint _touchPoint in e.GetTouchPoints(this.canvas1))
    if (_touchPoint.Action == TouchAction.Down)
        // Clear the canvas and capture the touch to it.

    else if (_touchPoint.Action == TouchAction.Move && e.GetPrimaryTouchPoint(this.canvas1) != null)
        // This is the first (primary) touch point. Just record its position.
        if (_touchPoint.TouchDevice.Id == e.GetPrimaryTouchPoint(this.canvas1).TouchDevice.Id)
            pt1.X = _touchPoint.Position.X;
            pt1.Y = _touchPoint.Position.Y;

        // This is not the first touch point. Draw a line from the first point to this one.
        else if (_touchPoint.TouchDevice.Id != e.GetPrimaryTouchPoint(this.canvas1).TouchDevice.Id)
            pt2.X = _touchPoint.Position.X;
            pt2.Y = _touchPoint.Position.Y;

            Line _line = new Line();
            _line.Stroke = new RadialGradientBrush(Colors.White, Colors.Black);
            _line.X1 = pt1.X;
            _line.X2 = pt2.X;
            _line.Y1 = pt1.Y;
            _line.Y2 = pt2.Y;
            _line.StrokeThickness = 2;

    else if (_touchPoint.Action == TouchAction.Up)
        // If this touch is captured to the canvas, release it.
        if (_touchPoint.TouchDevice.Captured == this.canvas1)

.NET Framework
Available since 4.0
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