Convex Hull Online

This sample demonstrates adding 3 or more graphic points on the map to call an ESRI.ArcGIS.Client.Tasks GeometryService that will return and display a convex hull graphic. A convex hull is the smallest polygon that completely encases a set (i.e. locus) of points.

To use the sample, add 3 or more points on the map and click the Generate Convex Hull button. A polygon containing all the points entered will be returned.

XAML

<UserControl x:Class="ArcGISWPFSDK.ConvexHull"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:esri="http://schemas.esri.com/arcgis/client/2009">
    <Grid x:Name="LayoutRoot">

        <Grid.Resources>
            <esri:SimpleMarkerSymbol x:Key="DefaultMarkerSymbol" Color="Red" Size="6" />
            <esri:SimpleFillSymbol x:Key="DefaultFillSymbol" Fill="#88FFFF00" BorderBrush="Yellow" />
            <LinearGradientBrush x:Key="PanelGradient" EndPoint="0.5,1" StartPoint="0.5,0">
                <LinearGradientBrush.RelativeTransform>
                    <TransformGroup>
                        <ScaleTransform CenterY="0.5" CenterX="0.5"/>
                        <SkewTransform CenterY="0.5" CenterX="0.5"/>
                        <RotateTransform Angle="176" CenterY="0.5" CenterX="0.5"/>
                        <TranslateTransform/>
                    </TransformGroup>
                </LinearGradientBrush.RelativeTransform>
                <GradientStop Color="#FF145787" Offset="0.16"/>
                <GradientStop Color="#FF3D7FAC" Offset="0.502"/>
                <GradientStop Color="#FF88C5EF" Offset="0.984"/>
            </LinearGradientBrush>
        </Grid.Resources>

        <esri:Map x:Name="MyMap" Extent="-100,25,-60,50">
            <esri:ArcGISTiledMapServiceLayer ID="StreetMapLayer" 
                      Url="http://services.arcgisonline.com/ArcGIS/rest/services/ESRI_Imagery_World_2D/MapServer"/>
            <esri:GraphicsLayer ID="InputGraphicsLayer" />
            <esri:GraphicsLayer ID="ConvexHullGraphicsLayer" />
        </esri:Map>

        <Grid HorizontalAlignment="Right" VerticalAlignment="Top" Margin="0,10,10,0" >
            <Rectangle Fill="{StaticResource PanelGradient}" Stroke="Gray"  RadiusX="10" RadiusY="10" Margin="0,0,0,5" >
                <Rectangle.Effect>
                    <DropShadowEffect/>
                </Rectangle.Effect>
            </Rectangle>
            <Rectangle Fill="#FFFFFFFF" Stroke="DarkGray" RadiusX="5" RadiusY="5" Margin="10,10,10,15" />
            <StackPanel Orientation="Vertical" Margin="30,20,20,30" >
                <TextBlock x:Name="ResponseTextBlock" Text="Add 3 or more points on the map and click the Generate Convex Hull button.  A polygon containing all the points entered will be returned. "
                           Width="400" TextAlignment="Left"  TextWrapping="Wrap" Foreground="Black"/>
                <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" >
                    <Button Content="Generate Convex Hull" Margin="0,5,5,0" x:Name="ConvexButton" 
                             Click="ConvexButton_Click" IsEnabled="False" />
                </StackPanel>
            </StackPanel>
        </Grid>

    </Grid>
</UserControl>

C#

using System.Linq;
using System.Windows;
using System.Windows.Controls;
using ESRI.ArcGIS.Client;
using ESRI.ArcGIS.Client.Tasks;

namespace ArcGISWPFSDK
{
    public partial class ConvexHull : UserControl
    {
        private Draw MyDrawObject;
        private GraphicsLayer outputGraphicsLayer;
        private GraphicsLayer inputGraphicsLayer;

        public ConvexHull()
        {
            InitializeComponent();

            MyDrawObject = new Draw(MyMap)
            {
                DrawMode = DrawMode.Point,
                IsEnabled = true
            };
            MyDrawObject.DrawComplete += MyDrawObject_DrawComplete;

            outputGraphicsLayer = MyMap.Layers["ConvexHullGraphicsLayer"] as GraphicsLayer;
            inputGraphicsLayer = MyMap.Layers["InputGraphicsLayer"] as GraphicsLayer;
        }

        private void MyDrawObject_DrawComplete(object sender, DrawEventArgs args)
        {
            outputGraphicsLayer.ClearGraphics();

            ESRI.ArcGIS.Client.Geometry.MapPoint point = args.Geometry as ESRI.ArcGIS.Client.Geometry.MapPoint;
            point.SpatialReference = MyMap.SpatialReference;
            Graphic graphic = new Graphic()
            {
                Symbol = LayoutRoot.Resources["DefaultMarkerSymbol"] as ESRI.ArcGIS.Client.Symbols.Symbol,
                Geometry = point
            };

            inputGraphicsLayer.Graphics.Add(graphic);

            if (inputGraphicsLayer.Graphics.Count >= 3)
                ConvexButton.IsEnabled = true;
        }

        private void ConvexButton_Click(object sender, RoutedEventArgs e)
        {
            ConvexButton.IsEnabled = false;
            outputGraphicsLayer.ClearGraphics();

            GeometryService geometryService =
                        new GeometryService("http://tasks.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer");
            geometryService.ConvexHullCompleted += GeometryService_ConvexHullCompleted;
            geometryService.Failed += GeometryService_Failed;

            geometryService.ConvexHullAsync(inputGraphicsLayer.ToList());
        }

        void GeometryService_ConvexHullCompleted(object sender, GeometryEventArgs e)
        {
            Graphic graphic = new Graphic()
            {
                Symbol = LayoutRoot.Resources["DefaultFillSymbol"] as ESRI.ArcGIS.Client.Symbols.Symbol,
                Geometry = e.Result
            };
            outputGraphicsLayer.Graphics.Add(graphic);

            ConvexButton.IsEnabled = true;
        }

        private void GeometryService_Failed(object sender, TaskFailedEventArgs e)
        {
            MessageBox.Show("Geometry Service error: " + e.Error);
        }
    }
}

VB.NET

Imports System.Linq
Imports System.Windows
Imports System.Windows.Controls
Imports ESRI.ArcGIS.Client
Imports ESRI.ArcGIS.Client.Tasks

Namespace ArcGISWPFSDK
    Partial Public Class ConvexHull
        Inherits UserControl
        Private MyDrawObject As Draw
        Private outputGraphicsLayer As GraphicsLayer
        Private inputGraphicsLayer As GraphicsLayer

        Public Sub New()
            InitializeComponent()

            MyDrawObject = New Draw(MyMap) With { _
             .DrawMode = DrawMode.Point, _
             .IsEnabled = True _
            }
            AddHandler MyDrawObject.DrawComplete, AddressOf MyDrawObject_DrawComplete

            outputGraphicsLayer = TryCast(MyMap.Layers("ConvexHullGraphicsLayer"), GraphicsLayer)
            inputGraphicsLayer = TryCast(MyMap.Layers("InputGraphicsLayer"), GraphicsLayer)
        End Sub

        Private Sub MyDrawObject_DrawComplete(sender As Object, args As DrawEventArgs)
            outputGraphicsLayer.ClearGraphics()

            Dim point As ESRI.ArcGIS.Client.Geometry.MapPoint = TryCast(args.Geometry, ESRI.ArcGIS.Client.Geometry.MapPoint)
            point.SpatialReference = MyMap.SpatialReference
            Dim graphic As New Graphic() With { _
             .Symbol = TryCast(LayoutRoot.Resources("DefaultMarkerSymbol"), ESRI.ArcGIS.Client.Symbols.Symbol), _
             .Geometry = point _
            }

            inputGraphicsLayer.Graphics.Add(graphic)

            If inputGraphicsLayer.Graphics.Count >= 3 Then
                ConvexButton.IsEnabled = True
            End If
        End Sub

        Private Sub ConvexButton_Click(sender As Object, e As RoutedEventArgs)
            ConvexButton.IsEnabled = False
            outputGraphicsLayer.ClearGraphics()

            Dim geometryService As New GeometryService("http://tasks.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer")
            AddHandler geometryService.ConvexHullCompleted, AddressOf GeometryService_ConvexHullCompleted
            AddHandler geometryService.Failed, AddressOf GeometryService_Failed

            geometryService.ConvexHullAsync(inputGraphicsLayer.ToList())
        End Sub

        Private Sub GeometryService_ConvexHullCompleted(sender As Object, e As GeometryEventArgs)
            Dim graphic As New Graphic() With { _
             .Symbol = TryCast(LayoutRoot.Resources("DefaultFillSymbol"), ESRI.ArcGIS.Client.Symbols.Symbol), _
             .Geometry = e.Result _
            }
            outputGraphicsLayer.Graphics.Add(graphic)

            ConvexButton.IsEnabled = True
        End Sub

        Private Sub GeometryService_Failed(sender As Object, e As TaskFailedEventArgs)
            MessageBox.Show("Geometry Service error: " & Convert.ToString(e.[Error]))
        End Sub
    End Class
End Namespace