Async
Contents
async und await
Task.Run()
using System;
using System.Threading;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private async void Button_Click(object sender, RoutedEventArgs e)
{
Console.WriteLine("Button_Click: " + Thread.CurrentThread.GetHashCode());
string p = await Task.Run(() => { return GetString(); });
myLabel.Content = p;
}
static string GetString()
{
//GetString wird nicht im UI Thread ausgeführt.
Console.WriteLine("GetStringStart: " + Thread.CurrentThread.GetHashCode());
System.Threading.Thread.Sleep(10000);
Console.WriteLine("GetStringEnd: " + Thread.CurrentThread.GetHashCode());
return "Hello World asynchronous";
}
}
}
Converting old style System.ComponentModel.AsyncCompletedEventArgs to new style
internal static class Extension
{
private static void TransferCompletion<T>(
TaskCompletionSource<T> tcs, System.ComponentModel.AsyncCompletedEventArgs e,
Func<T> getResult)
{
if (e.Error != null)
{
tcs.TrySetException(e.Error);
}
else if (e.Cancelled)
{
tcs.TrySetCanceled();
}
else
{
tcs.TrySetResult(getResult());
}
}
public static Task<loginCompletedEventArgs> LoginAsyncTask(this YChatWebService.WebServiceControllerPortTypeClient client, string userName, string password)
{
var tcs = new TaskCompletionSource<loginCompletedEventArgs>();
client.loginCompleted += (s, e) => TransferCompletion(tcs, e, () => e);
client.loginAsync(userName, password);
return tcs.Task;
}
}
Avoid thread switching
async Task SomeMethod()
{
for (int i = 0; i < 1000000; i++)
{
await SomeOtherMethod().ConfigureAwait(false);
}
}
async Task SomeOtherMethod()
{
await ...
}
Parallelism
Serielle Abarbeitung:
private async void button_Click(object sender, EventArgs e)
{
this.pictureBox1.Image = await GetImage("http://imageurl1");
this.pictureBox2.Image = await GetImage("http://imageurl2");
this.pictureBox3.Image = await GetImage("http://imageurl3");
}
Parallel 1:
private async void button_Click(object sender, EventArgs e)
{
Task<Image> task1 = GetImage("http://imageurl1"); //Download startet beim Aufruf GetImage
Task<Image> task2 = GetImage("http://imageurl2");
Task<Image> task3 = GetImage("http://imageurl3");
this.pictureBox1.Image = await task1;
this.pictureBox2.Image = await task2;
this.pictureBox3.Image = await task3;
}
Parallel 2:
private async void button_Click(object sender, EventArgs e)
{
Task<Image> task1 = GetImage("http://imageurl1");
Task<Image> task2 = GetImage("http://imageurl2");
Task<Image> task3 = GetImage("http://imageurl3");
await Task.WhenAll(task1, task2, task3);
this.pictureBox1.Image = task1.Result;
this.pictureBox2.Image = task2.Result;
this.pictureBox3.Image = task3.Result;
}