InvalidOperationException：在ImageOffsetProperty上暂停调度程序处理 [英] InvalidOperationException: dispatcher processing is suspended on ImageOffsetProperty

问题描述

我正在使用C＃和WPF，并试图在屏幕上滑动图像条。老实说，我从Internet上的一些代码示例中获取了代码，并从中获取了所需的部分。

I am using C# and WPF and am trying to slide an image strip along the screen. I am being honest, I got the code from some code sample on the Internet and took the parts I needed from it.

public double ImageOffset
{
    get
    {
        try
        {
            return (double)this.Dispatcher.Invoke(
               System.Windows.Threading.DispatcherPriority.Background,
               (DispatcherOperationCallback)delegate 
               { return GetValue(ImageOffsetProperty); }, ImageOffsetProperty);
        }
        catch
        {
            return (double)this.GetValue(ImageOffsetProperty);
        }
    }

    set
    {
        this.Dispatcher.BeginInvoke(DispatcherPriority.Background,
            (SendOrPostCallback)delegate 
            { SetValue(ImageOffsetProperty, (object)value); },
            (object)value);
    }
}

有时程序尝试获取ImageOffsetProperty和 InvalidOperationException：调度程序处理暂停时无法执行此操作发生，而且我不知道如何解决。

Sometimes when the program tries to get the ImageOffsetProperty an InvalidOperationException: Cannot perform this operation while dispatcher processing is suspended happens and I have no idea how to fix it.

I还尝试了 Dispatcher.BeginInvoke ，将ImageOffsetProperty安全地保存在Double中，然后将其返回，但始终返回0。

I also tried Dispatcher.BeginInvoke, safe the ImageOffsetProperty in a Double and then return it, but it always returned 0.

是什么原因导致 InvalidOperationException ？

推荐答案

如何删除所有 Background 之类的东西，然后像这样编写一个标准的依赖项属性包装器：

How about dropping all the Background stuff and just write a standard dependency property wrapper like this:

public double ImageOffset
{
    get { return (double)GetValue(ImageOffsetProperty); }
    set { SetValue(ImageOffsetProperty, value); }
}

从后台线程设置属性后，将赋值放入 Dispatcher.Invoke 或 Dispatcher.BeginInvoke 呼叫。

When the property is set from a background thread, put the assignment in a Dispatcher.Invoke or Dispatcher.BeginInvoke call.

替换

obj.ImageOffset = someOffset;

by

Dispatcher.Invoke(() => obj.ImageOffset = someOffset);

或

Application.Current.Dispatcher.Invoke(() => obj.ImageOffset = someOffset);

如果您无法直接访问 Dispatcher 属性。

if you don't have direct access to the Dispatcher property of some UI element.

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