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StreamGeometryContext Class

Describes a geometry using drawing commands. This class is used with the StreamGeometry class to create a lightweight geometry that does not support data binding, animation, or modification.

System.Object
  System.Windows.Threading.DispatcherObject
    System.Windows.Media.StreamGeometryContext

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

public abstract class StreamGeometryContext : DispatcherObject, 
	IDisposable

The StreamGeometryContext type exposes the following members.

  NameDescription
Public propertyDispatcherGets the Dispatcher this DispatcherObject is associated with. (Inherited from DispatcherObject.)
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  NameDescription
Public methodArcToDraws an arc to the specified point.
Public methodBeginFigureSpecifies the starting point for a new figure.
Public methodBezierToDraws a Bezier curve to the specified point.
Public methodCheckAccessDetermines whether the calling thread has access to this DispatcherObject. (Inherited from DispatcherObject.)
Public methodCloseCloses this context and flushes its content so that it can be rendered.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodLineToDraws a straight line to the specified Point.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodPolyBezierToDraws one or more connected Bezier curves.
Public methodPolyLineToDraws one or more connected straight lines.
Public methodPolyQuadraticBezierToDraws one or more connected quadratic Bezier curves.
Public methodQuadraticBezierToDraws a quadratic Bezier curve.
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodVerifyAccessEnforces that the calling thread has access to this DispatcherObject. (Inherited from DispatcherObject.)
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  NameDescription
Explicit interface implemetationPrivate methodIDisposable.DisposeThis member supports the Windows Presentation Foundation (WPF) infrastructure and is not intended to be used directly from your code.
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ExceptionCondition
InvalidOperationException

An attempt was made to add a segment without starting a figure by calling the BeginFigure method.

StreamGeometry is light-weight alternative to PathGeometry for creating geometric shapes. Use a StreamGeometry when you need to describe a complex geometry but do not want the overhead of supporting data binding, animation, or modification. For example, because of its efficiency, the StreamGeometry class is a good choice for describing adorners.

The following example uses attribute syntax to create a triangular StreamGeometry in XAML.

<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <StackPanel>

    <Path Data="F0 M10,100 L100,100 100,50Z" 
      StrokeThickness="1" Stroke="Black"/>

  </StackPanel>
</Page>

For more information about StreamGeometry attribute syntax, see the Path Markup Syntax page.

The next example uses a StreamGeometry to define a triangle in code. First, the example creates a StreamGeometry, then obtains a StreamGeometryContext and uses it to describe the triangle.

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;

namespace SDKSample
{
    // Use StreamGeometry with StreamGeometryContext to define a triangle shape. 
    public partial class StreamGeometryTriangleExample : Page
    {
        public StreamGeometryTriangleExample()
        {
            // Create a path to draw a geometry with.
            Path myPath = new Path();
            myPath.Stroke = Brushes.Black;
            myPath.StrokeThickness = 1;

            // Create a StreamGeometry to use to specify myPath.
            StreamGeometry geometry = new StreamGeometry();
            geometry.FillRule = FillRule.EvenOdd;

            // Open a StreamGeometryContext that can be used to describe this StreamGeometry  
            // object's contents. 
            using (StreamGeometryContext ctx = geometry.Open())
            {

                // Begin the triangle at the point specified. Notice that the shape is set to  
                // be closed so only two lines need to be specified below to make the triangle.
                ctx.BeginFigure(new Point(10, 100), true /* is filled */, true /* is closed */);

                // Draw a line to the next specified point.
                ctx.LineTo(new Point(100, 100), true /* is stroked */, false /* is smooth join */);

                // Draw another line to the next specified point.
                ctx.LineTo(new Point(100, 50), true /* is stroked */, false /* is smooth join */);
            }

            // Freeze the geometry (make it unmodifiable) 
            // for additional performance benefits.
            geometry.Freeze();

            // Specify the shape (triangle) of the Path using the StreamGeometry.
            myPath.Data = geometry;

            // Add path shape to the UI.
            StackPanel mainPanel = new StackPanel();
            mainPanel.Children.Add(myPath);
            this.Content = mainPanel;
        }
    }
}

The next example creates a method that uses a StreamGeometry and StreamGeometryContext to define a geometric shape based on specified parameters.

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;

namespace SDKSample
{
    public partial class StreamGeometryExample : Page
    {
        public StreamGeometryExample()
        {
            // Create a path to draw a geometry with.
            Path myPath = new Path();
            myPath.Stroke = Brushes.Black;
            myPath.StrokeThickness = 1;

            // Create a StreamGeometry to use to specify myPath.
            StreamGeometry theGeometry = BuildRegularPolygon(new Point(200, 200), 200, 8, 0);
            theGeometry.FillRule = FillRule.EvenOdd;

            // Freeze the geometry (make it unmodifiable) 
            // for additional performance benefits.
            theGeometry.Freeze();

            // Use the StreamGeometry returned by the BuildRegularPolygon to  
            // specify the shape of the path.
            myPath.Data = theGeometry;

            // Add path shape to the UI.
            StackPanel mainPanel = new StackPanel();
            mainPanel.Children.Add(myPath);
            this.Content = mainPanel;
        }

        StreamGeometry BuildRegularPolygon(Point c, double r, int numSides, double offsetDegree)
        {
            // c is the center, r is the radius, 
            // numSides the number of sides, offsetDegree the offset in Degrees. 
            // Do not add the last point.

            StreamGeometry geometry = new StreamGeometry();

            using (StreamGeometryContext ctx = geometry.Open())
            {
                ctx.BeginFigure(new Point(), true /* is filled */, true /* is closed */);

                double step = 2 * Math.PI / Math.Max(numSides, 3);
                Point cur = c;

                double a = Math.PI * offsetDegree / 180.0;
                for (int i = 0; i < numSides; i++, a += step)
                {
                    cur.X = c.X + r * Math.Cos(a);
                    cur.Y = c.Y + r * Math.Sin(a);
                    ctx.LineTo(cur, true /* is stroked */, false /* is smooth join */);
                }
            }

            return geometry;
        }
    }
}

.NET Framework

Supported in: 4.5.3, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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