WPF

<Window x:Class="SampleApplication.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Sample" Height="600" Width="922" WindowState="Maximized" Loaded="Window_Loaded">
    <Grid>
        <Canvas Name="myCanvas" Background="AliceBlue">
            <Polygon Name="polygonFill" Stretch="Fill" Points="177,177 0,177 88.5,0" Fill="Transparent" Stroke="Black" StrokeThickness="2" Canvas.Left="100" Canvas.Top="100" 
                     Height="{Binding ElementName=sliderStretchFill,Path=Value}"
                     />
            <Slider Name="sliderStretchFill" Width="150" Height="22" Canvas.Left="112" Canvas.Top="35" Minimum="10" Maximum="200" Value="100" />
            <Label Canvas.Left="100" Canvas.Top="66" Height="28" Name="lblStretchFill" Width="77">Stretch="Fill"</Label>
            <Label Canvas.Left="175" Canvas.Top="66" >Height=</Label>
            <Label Canvas.Left="215" Canvas.Top="66" Height="28" Name="lblStretchHeight" Width="29" Content="{Binding ElementName=sliderStretchFill,Path=Value}"/>
            <Polygon Name="polygonNone" Stretch="None" Points="177,177 0,177 88.5,0" Fill="Transparent" Stroke="Black" StrokeThickness="2" Canvas.Left="700" Canvas.Top="100" 
                     Height="{Binding ElementName=sliderStretchNone,Path=Value}"
                     />
            <Slider Name="sliderStretchNone" Width="150" Height="22" Canvas.Left="712" Canvas.Top="35" Minimum="10" Maximum="200" Value="100" />
            <Label Canvas.Left="700" Canvas.Top="66" Height="28" Name="lblStretchNone" Width="91">Stretch="None"</Label>
            <Label Canvas.Left="785" Canvas.Top="66" >Height=</Label>
            <Label Canvas.Left="825" Canvas.Top="66" Height="28" Name="lblStretchNoneHeight" Width="29" Content="{Binding ElementName=sliderStretchNone,Path=Value}"/>
        </Canvas>
    </Grid>
</Window>

namespace SampleApplication
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
        }
        Selection selection;
        AdornerLayer adornerLayer;

        void AddAdornerLayerToPolygonFill()
        {
            adornerLayer = AdornerLayer.GetAdornerLayer(polygonFill);
            selection = new Selection(polygonFill);
            adornerLayer.Add(selection);
        }
        void AddAdornerLayerToPolygonNone()
        {
            adornerLayer = AdornerLayer.GetAdornerLayer(polygonNone);
            selection = new Selection(polygonNone);
            adornerLayer.Add(selection);
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            AddAdornerLayerToPolygonFill();
            AddAdornerLayerToPolygonNone();
        }
    }
}






namespace SampleApplication
{
    class Selection : Adorner
    {
        VisualCollection visualChildren;
        Polygon polygon;
        Point point;
        ArrayList thumbArrray = new ArrayList();
        Thumb thumb;

        public Selection(UIElement adornedElement)
            : base(adornedElement)
        {
            visualChildren = new VisualCollection(this);

            polygon = (Polygon)adornedElement;
            for (int i = 0; i < polygon.Points.Count; i++)
            {
                point = polygon.Points[i];
                thumb = new Thumb();
                BuildCorner(ref thumb, Cursors.SizeNESW);
                thumb.Tag = i;
                thumb.DragDelta += new DragDeltaEventHandler(thumb_DragDelta);
                thumbArrray.Add(thumb);
            }
        }

        void thumb_DragDelta(object sender, DragDeltaEventArgs e)
        {
            FrameworkElement adornedElement = this.AdornedElement as FrameworkElement;
            polygon = (Polygon)adornedElement;

            thumb = (Thumb)sender;
            point = polygon.Points[(int)thumb.Tag];

            point.X += e.HorizontalChange;
            point.Y += e.VerticalChange;

            polygon.Points[(int)thumb.Tag] = point;

            adornedElement = polygon;
            InvalidateArrange();
        }
        void BuildCorner(ref Thumb cornerThumb, Cursor customizedCursor)
        {
            cornerThumb = new Thumb();
            cornerThumb.Height = cornerThumb.Width = 10;
            cornerThumb.Background = Brushes.Black;
            cornerThumb.Cursor = customizedCursor;
            cornerThumb.Opacity = 0.80;
            visualChildren.Add(cornerThumb);
        }
        protected override Size ArrangeOverride(Size finalSize)
        {
            FrameworkElement adornedElement = this.AdornedElement as FrameworkElement;
            polygon = (Polygon)adornedElement;

            for (int i = 0; i < polygon.Points.Count; i++)
            {
                point = polygon.Points[i];
                thumb = (Thumb)thumbArrray[i];
                thumb.Arrange(new Rect(point.X - 5, point.Y - 5, 10, 10));
            }
            return finalSize;
        }

        protected override Visual GetVisualChild(int index) { return visualChildren[index]; }

        protected override int VisualChildrenCount { get { return visualChildren.Count; } }
    }
}