c# - 无法将类型“System.EventHandler”隐式转换为“System.EventHandler”

Question

I am trying to fade a text box within specified time. This code works on Windows Phone but it doesn't work in a Windows 8 application. I made changes to fix as many errors as possible. but I couldn't resolve one of them: cannot implicitly convert type 'System.EventHandler' to 'System.EventHandler<object>" arises on the expression sb.Completed += ehl. The full function is below:

    public static void Fade(UIElement target, double ValueFrom, double ValueTo, double Duration)
    {
        DoubleAnimation da = new DoubleAnimation();
        da.From = ValueFrom;
        da.To = ValueTo;
        da.Duration = TimeSpan.FromSeconds(Duration);
        da.AutoReverse = false;

        Windows.UI.Xaml.Media.Animation.Storyboard.SetTargetProperty(da, "opacity");

        Windows.UI.Xaml.Media.Animation.Storyboard.SetTarget(da, target);

        Windows.UI.Xaml.Media.Animation.Storyboard sb = new Windows.UI.Xaml.Media.Animation.Storyboard();
        sb.Children.Add(da);

        EventHandler ehl = null;
        ehl = (s, args) =>
        {

            sb.Stop();
            sb.Completed+= ehl; //error occurs here
            target.Opacity = ValueTo;
        };
        sb.Completed += ehl; //error occurs here

        sb.Begin();
    }

score 2 · Accepted Answer

Completed事件的类型是EventHandler<object>，但您声明事件处理程序是类型EventHandler，而不是EventHandler<object>。

这正是错误消息告诉您的内容，因此您应该将事件处理程序的类型更改为 EventHandler<object>.

顺便说一句，事件处理程序sb.Completed+= ehl; 内的行似乎很奇怪。每次调用事件处理程序时，您基本上都会再次将处理程序附加到事件。

c# - 无法将类型“System.EventHandler”隐式转换为“System.EventHandler”

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