WPF 中实现 Winfrom 中 Application.DoEvents() 方法

熟悉 Winfrom 中 Application.DoEvents() 方法的朋友一定用过此方法，此方法可以立即处理当前在消息队列中的所有 Windows 消息。 如在一个按钮单击事件中，需要每一秒改变label的Text属性，如下代码：

     private void button1_Click(object sender, EventArgs e)
     {
         for (int i = 0; i < 50; i++)
{
             Thread.Sleep(500);
             this.label1.Text = i.ToString();
}
     }

private void button1_Click(object sender, EventArgs e) { for (int i = 0; i < 50; i++) { Thread.Sleep(500); this.label1.Text = i.ToString(); } }

编译运行，单击按钮，你并不会见到lable一直改变，等到执行完，你只会看见49。而加上 Application.DoEvents() 方法则可以看到一直更改的文本

private void button1_Click(object sender, EventArgs e)
{
    for (int i = 0; i < 50; i++)

        Thread.Sleep(500);
        this.label1.Text = i.ToString();
        Application.DoEvents();

}

private void button1_Click(object sender, EventArgs e) { for (int i = 0; i < 50; i++) { Thread.Sleep(500); this.label1.Text = i.ToString(); Application.DoEvents(); } }

好了，废话不多说了，不明白的可以参考 Application.DoEvents 方法。

      在 WPF 中没有 Application.DoEvents() 方法，看下面实现代码：

public static class DispatcherHelper
{
    [SecurityPermissionAttribute(SecurityAction.Demand, Flags = SecurityPermissionFlag.UnmanagedCode)]
    public static void DoEvents()
    {
        DispatcherFrame frame = new DispatcherFrame();
        Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(ExitFrames), frame);
        try { Dispatcher.PushFrame(frame); }
        catch (InvalidOperationException) { }
    }
    private static object ExitFrames(object frame)
    {
        ((DispatcherFrame)frame).Continue = false;
        return null;
    }
}

public static class DispatcherHelper { [SecurityPermissionAttribute(SecurityAction.Demand, Flags = SecurityPermissionFlag.UnmanagedCode)] public static void DoEvents() { DispatcherFrame frame = new DispatcherFrame(); Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(ExitFrames), frame); try { Dispatcher.PushFrame(frame); } catch (InvalidOperationException) { } } private static object ExitFrames(object frame) { ((DispatcherFrame)frame).Continue = false; return null; } }

调用：

DispatcherHelper.DoEvents();