Task-based Asynchronous (TAP) operation Online

This sample demonstrates using the Task-based Asynchronous (TAP) operation available in .NET Framework 4 for a QueryTask.

XAML

<UserControl x:Class="ArcGISWPFSDK.TaskBasedAsync"
    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:ArcGISTiledMapServiceLayer ID="MyLayer" 
                Url="http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer" />
            <esri:GraphicsLayer ID="MyGraphics"
                                Renderer="{StaticResource FillRenderer}"/>
    </esri:Map>
        <Border HorizontalAlignment="Right" VerticalAlignment="Top" Margin="0,10,143,0" Padding="5" Background="White" 
                BorderBrush="Black" BorderThickness="1" Width="219">
            <Border.Effect>
                <DropShadowEffect />
            </Border.Effect>
            <StackPanel Orientation="Horizontal" VerticalAlignment="Top" HorizontalAlignment="Left" 
                    Width="330" Height="50" Margin="5">
                <Button Content="QueryTask using Task Based Async" Margin="5" Width="188" Click="Button_Click_1" />       
            </StackPanel>
        </Border>
    </Grid>
</UserControl>

C#

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

namespace ArcGISWPFSDK
{
    public partial class TaskBasedAsync : UserControl
    {
        public TaskBasedAsync()
        {
            InitializeComponent();
        }

        private void Button_Click_1(object sender, System.Windows.RoutedEventArgs e)
        {
            ClearResults();

            QueryTask queryTask = new QueryTask("http://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/3");

            // Call ExecuteTaskAsync and handle add the results to the map in the Continuation.
            Task task = queryTask.ExecuteTaskAsync(new Query()
            {
                Where = "1=1",
                ReturnGeometry = true,
                OutSpatialReference = MyMap.SpatialReference
            }).ContinueWith((queryResultTask) =>
            {
                if (queryResultTask.IsFaulted)
                {
                    MessageBox.Show(queryResultTask.Exception.Message);
                }
                else if (queryResultTask.Result != null)
                {
                    AddResultsToMap(queryResultTask.Result.FeatureSet.Features);
                }
            }, TaskScheduler.FromCurrentSynchronizationContext());
        }

        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.Tasks
Imports System.Collections.Generic
Imports System.Threading.Tasks
Imports System.Windows.Controls

Namespace ArcGISWPFSDK
    Partial Public Class TaskBasedAsync
        Inherits UserControl
        Public Sub New()
            InitializeComponent()
        End Sub

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

        Private Function UsingTaskBased() As Task
            ClearResults()


            Dim t = New QueryTask("http://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/3")

            Dim task As Task(Of QueryResult) = t.ExecuteTaskAsync(New Query() With { _
                 .Where = "1=1", _
                 .ReturnGeometry = True, _
                 .OutSpatialReference = MyMap.SpatialReference _
            })


            task.ContinueWith(Function(r)
                                           If r.IsFaulted Then

                                               Dim ex = r.Exception
                                           ElseIf r.Result IsNot Nothing Then

                                               AddResultsToMap(r.Result.FeatureSet.Features)
                                           End If

                                       End Function, TaskScheduler.FromCurrentSynchronizationContext())
        End Function

        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