TAP operation using Async and Await keywords Online

This sample demonstrates using the new awaitable TAP operation using async and wait keywords availiable in .NET Framework 4.5 for a QueryTask.

XAML

<UserControl x:Class="ArcGISWPFSDK.AsyncAwait"
    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 Async Await" Margin="5" Width="188" Click="Button_Click_1" />       
            </StackPanel>
        </Border>
    </Grid>
</UserControl>

C#

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

namespace ArcGISWPFSDK
{
    public partial class AsyncAwait : UserControl
    {
        public AsyncAwait()
        {
            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");

            /*
             * If using .NET 4.5 / 4.5.1 (or .NET 4.0 with the Async Targeting Pack for Visual Studio 11) can simply "await" methods which return a Task.
             * However - this sample application is compiled as .NET 4.0 and therefore uses ContinueWith as an alternative. 
            */
            //QueryResult queryResult = null;
            //try
            //{
            //    queryResult = await queryTask.ExecuteTaskAsync(new Query()
            //    {
            //        Where = "1=1",
            //        ReturnGeometry = true,
            //        OutSpatialReference = MyMap.SpatialReference
            //    });
            //    AddResultsToMap(queryResult.FeatureSet.Features);
            //}
            //catch (AggregateException ex)
            //{
            //    var innermostExceptions = ex.Flatten().InnerExceptions;
            //    if (innermostExceptions != null && innermostExceptions.Count > 0)
            //        MessageBox.Show(innermostExceptions[0].Message);
            //    else
            //        MessageBox.Show(ex.Message);
            //}

            Task task = queryTask.ExecuteTaskAsync(new Query()
            {
                Where = "1=1",
                ReturnGeometry = true,
                OutSpatialReference = MyMap.SpatialReference
            }).ContinueWith((r) =>
            {
                if (r.IsFaulted)
                {
                    var ex = r.Exception;

                }
                else if (r.Result != null)
                {
                    AddResultsToMap(r.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 System.Windows.Controls
Imports System.Windows
Imports ESRI.ArcGIS.Client
Imports ESRI.ArcGIS.Client.Tasks
Imports System.Collections.Generic
Imports System.Threading.Tasks

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

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

        Private Async Function UsingAsyncAwait() As Task
            ClearResults()
            Dim t = New QueryTask("http://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/3")
            Dim b As QueryResult = Nothing
            Try
                b = Await t.ExecuteTaskAsync(New Query() With { _
                     .Where = "1=1", _
                     .ReturnGeometry = True, _
                     .OutSpatialReference = MyMap.SpatialReference _
                })
                AddResultsToMap(b.FeatureSet.Features)
            Catch ex As AggregateException
                Dim innermostExceptions = ex.Flatten().InnerExceptions
                If innermostExceptions IsNot Nothing AndAlso innermostExceptions.Count > 0 Then
                    MessageBox.Show(innermostExceptions(0).Message)
                Else
                    MessageBox.Show(ex.Message)
                End If
            End Try
        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