Joining the Mouse clicks with curves and forming shapes

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C#

WPF

C#4.0

Hello,

I am displaying the images in mediaelement.
Now if i do clicks on the image and select draw shape button the clicked positions should join and form a shape. here iam using Quadraticbezier curves for joing the mous clicks.

When i do odd no. of clicks on the image and select draw shape. the shape is coming perfectly but if i do even no. of clicks the curve is forming without joining the starting point and ending point.
why is this happening plz any find where iam going wrong
code:

void Mediaelement1_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {

            checkPoints.Add(Mouse.GetPosition(mediaelement1));
        }

Drawshape button code:

SolidColorBrush bgBrush = new SolidColorBrush();
		bgBrush.Color = Colors.Transparent;
		SolidColorBrush borderBrush = new SolidColorBrush();
		borderBrush.Color = Colors.Black;
					
			Path polyPath = new Path();
			polyPath.Stroke = borderBrush;
			polyPath.StrokeThickness = 1;
			polyPath.Fill = bgBrush;
					
			GeometryGroup polyGeometryGroup = new GeometryGroup();
					
			PathFigure pLineFigure = new PathFigure();
	PolyQuadraticBezierSegment PQSegment=new PolyQuadraticBezierSegment ();
					
					
			foreach(var itr in checkPoints)
				{
					PQSegment.Points.Add(itr);
					
				}
					
					
		PQSegment.Points.Add( checkPoints[0]);
		Point startPoint= checkPoints[0];
		pLineFigure.StartPoint = new Point(startPoint.X,startPoint.Y);
		pLineFigure.Segments.Add( PQSegment);
		PathGeometry pGeometry = new PathGeometry();
		pGeometry.Figures.Add(pLineFigure);
					
		polyGeometryGroup.Children.Add(pGeometry);
					
	polyPath.Data = polyGeometryGroup;					
										
					
		this .mediasp.Children.Add (polyPath);
					
			checkPoints.Clear();
}

Plz anyone explain why even no. of clicks are not joininmg startpoint and end point while forming shape.