Event-based Asynchronous Pattern (EAP) with Inline Lambdas

This sample demonstrates using the Event-based Asynchronous Pattern (EAP) with inline lambdas for a QueryTask on local data.

XAML

<UserControl x:Class="ArcGISWPFSDK.LocalEventBasedAsyncLambda"
    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>
    <Grid.Resources>
        <esri:SimpleFillSymbol x:Key="RedFillSymbol"
                                   Fill="#66FF0000"
                                   BorderBrush="Red"
                                   BorderThickness="2" />
        <esri:SimpleRenderer x:Key="FillRenderer"
                                 Symbol="{StaticResource RedFillSymbol}" />
    </Grid.Resources>
        <esri:Map x:Name="MyMap" UseAcceleratedDisplay="True" WrapAround="True" Background="#FFE3E3E3">
            <esri:ArcGISLocalTiledLayer ID="BaseMap" Path="..\Data\TPKs\Topographic.tpk"/>
            <esri:GraphicsLayer ID="MyGraphics"
                                Renderer="{StaticResource FillRenderer}"/>
    </esri:Map>
        <Border HorizontalAlignment="Right" VerticalAlignment="Top" Margin="0,10,133,0" Padding="5" Background="White" 
                BorderBrush="Black" BorderThickness="1" Width="229">
            <Border.Effect>
                <DropShadowEffect />
            </Border.Effect>
            <StackPanel Orientation="Horizontal" VerticalAlignment="Top" HorizontalAlignment="Left" 
                    Width="330" Height="50" Margin="5">
                <Button x:Name="button1"  Content="QueryTask using Event Based Async" Margin="5" Width="199" Click="Button_Click_1" IsEnabled="False"/>       
            </StackPanel>
        </Border>
    </Grid>
</UserControl>

C#

using ESRI.ArcGIS.Client;
using ESRI.ArcGIS.Client.Local;
using ESRI.ArcGIS.Client.Tasks;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;

namespace ArcGISWPFSDK
{
    public partial class LocalEventBasedAsyncLambda : UserControl
    {
        LocalMapService _localMapService;

        public LocalEventBasedAsyncLambda()
        {
            InitializeComponent();

            _localMapService = new LocalMapService(@"..\Data\MPKS\USCitiesStates.mpk");

            // Use in-line Lambda expression to handle the async delegate callback.
            _localMapService.StartAsync((localMapService) =>
            {
                button1.IsEnabled = true;
            });
        }

        private void Button_Click_1(object sender, System.Windows.RoutedEventArgs e)
        {
            ClearResults();
            QueryTask queryTask = new QueryTask(_localMapService.UrlMapService + "/2");

            // Use in-line Lambda expression to handle the ExecuteCompleted event.
            queryTask.ExecuteCompleted += (a, b) =>
            {
                AddResultsToMap(b.FeatureSet.Features);
            };

            // Use in-line Lambda expression to handle the Failed event.
            queryTask.Failed += (a, b) =>
            {
                if (b.Error != null)
                    MessageBox.Show(b.Error.Message);
            };

            // Call Execute Async after the in-line handlers have been declared.
            queryTask.ExecuteAsync(new Query()
            {
                Where = "1=1",
                ReturnGeometry = true,
                OutSpatialReference = MyMap.SpatialReference
            });
        }

        private void ClearResults()
        {
            GraphicsLayer graphicsLayer = MyMap.Layers["MyGraphics"] as GraphicsLayer;
            graphicsLayer.Graphics.Clear();
        }

        private void AddResultsToMap(IList<Graphic> features)
        {
            GraphicsLayer graphicsLayer = MyMap.Layers["MyGraphics"] as GraphicsLayer;
            graphicsLayer.Graphics.AddRange(features);
            MyMap.ZoomTo(graphicsLayer.FullExtent);
        }
    }
}

VB.NET

Imports ESRI.ArcGIS.Client
Imports ESRI.ArcGIS.Client.Local
Imports ESRI.ArcGIS.Client.Tasks
Imports System.Collections.Generic
Imports System.Windows
Imports System.Windows.Controls

Namespace ArcGISWPFSDK
    Partial Public Class LocalEventBasedAsyncLambda
        Inherits UserControl
        Private _mapService As LocalMapService

        Public Sub New()
            InitializeComponent()

            CreateMapServiceAsync()
        End Sub

        Private Sub Button_Click_1(sender As Object, e As System.Windows.RoutedEventArgs)
            UsingEventBasedLambda()
        End Sub

        Public Sub CreateMapServiceAsync()

            LocalMapService.GetServiceAsync("..\Data\MPKS\USCitiesStates.mpk", Function(localMapService__1)
                                                                                            _mapService = localMapService__1

                                                                                            button1.IsEnabled = True

                                                                                        End Function)

        End Sub

        Private Sub UsingEventBasedLambda()

            ClearResults()
            Dim t = New QueryTask(Convert.ToString(_mapService.UrlMapService) & "/2")
            t.ExecuteCompleted += Function(a, b)
                                               AddResultsToMap(b.FeatureSet.Features)

                                           End Function
            t.Failed += Function(a, b)
                                     If b.[Error] IsNot Nothing Then
                                         MessageBox.Show(b.[Error].Message)
                                     End If

                                 End Function
            t.ExecuteAsync(New Query() With { _
                .Where = "1=1", _
                 .ReturnGeometry = True, _
             .OutSpatialReference = MyMap.SpatialReference _
            })
        End Sub

        Private Sub ClearResults()
            Dim l = TryCast(MyMap.Layers("MyGraphics"), GraphicsLayer)
            l.Graphics.Clear()
        End Sub

        Private Sub AddResultsToMap(features As IList(Of Graphic))
            Dim l = TryCast(MyMap.Layers("MyGraphics"), GraphicsLayer)
            l.Graphics.AddRange(features)
            MyMap.ZoomTo(l.FullExtent)
        End Sub
    End Class
End Namespace