C# 多线程 05-使用 C#6.0 06-避免使用捕获的同步上下文

🏷️ 《C# 多线程》

避免使用捕获的同步上下文

/// <summary>
/// 避免使用捕获的同步上下文
/// </summary>
/// <param name="args"></param>
[STAThread]
static void Main(string[] args)
{
    var app = new Application();
    var win = new Window();
    var panel = new StackPanel();
    var button = new Button();

    _label = new Label();
    _label.FontSize = 32;
    _label.Height = 200;

    button.Height = 100;
    button.FontSize = 32;
    button.Content = new TextBlock { Text = "开始异步操作" };
    button.Click += Click;

    panel.Children.Add(_label);
    panel.Children.Add(button);

    win.Content = panel;
    app.Run(win);

    Console.ReadLine();
}

private static Label _label;

static async void Click(object sender, EventArgs e)
{
    _label.Content = new TextBlock { Text = "计算中......" };
    TimeSpan resultWithContent = await Test();
    TimeSpan resultNoContent = await TestNoContent();
    //TimeSpan resultNoContent = await TestNoContent().ConfigureAwait(false);

    var sb = new StringBuilder();
    sb.AppendLine($"With the content: {resultWithContent}");
    sb.AppendLine($"Without the content: {resultNoContent}");
    sb.AppendLine($"Ratio: {resultWithContent.TotalMilliseconds / resultNoContent.TotalMilliseconds:0.00}");

    _label.Content = new TextBlock { Text = sb.ToString() };
}

static async Task<TimeSpan> Test()
{
    const int iterationsNumber = 100000;
    var sw = new Stopwatch();
    sw.Start();
    for (int i = 0; i < iterationsNumber; i++)
    {
        var t = Task.Run(() => { });
        await t;
    }
    sw.Stop();
    return sw.Elapsed;
}

static async Task<TimeSpan> TestNoContent()
{
    const int interationsNumber = 100000;
    var sw = new Stopwatch();
    sw.Start();
    for (int i = 0; i < interationsNumber; i++)
    {
        var t = Task.Run(() => { });
        // 将 continueOnCapturedContext 指定为 false，不使用捕获的同步上下文运行后续操作代码
        await t.ConfigureAwait(continueOnCapturedContext: false);
    }
    sw.Stop();
    return sw.Elapsed;
}

运行结果

With the content: 00:00:04.5821377
Without the content: 00:00:02.4224249
Ratio: 1.89

如果在运行时不停的改变窗体大小，运行结果的比率会显著的变大：

With the content: 00:00:16.0775755
Without the content: 00:00:03.2937352
Ratio: 4.88