Dispatcher.Invoke与匿名委托工作在Silverlight但不是WPF [英] Dispatcher.Invoke with anonymous delegate works in Silverlight but not WPF

问题描述

在Silverlight 4中我有已经完成的事件的异步定制服务类。 Completed事件里面我把返回的数据，并通过像这样调用一个方法填充：

In Silverlight 4 I have a custom service class which has an asynchronous Completed event. Inside the Completed event I take the returned data and invoke a populate method via something like this:

private void service_Completed(object sender, CompletedEventArgs args)
{
    Dispatcher.BeginInvoke(() => populateInbox(args.Jobs));
}

private void populateInbox(List<JobViewModel> jobs)
{
    inbox.DataContext = jobs;
}

的的BeginInvoke在SL4然而，当我把它移植到WPF我收到以下错误的作品，

无法转换拉姆达前pression键入'System.Delegate'，因为它不是一个委托类型

Cannot convert lambda expression to type 'System.Delegate' because it is not a delegate type

我试图将其更改为直列，匿名paramaterized委托：

I tried changing it to an in-line, anonymous, paramaterized delegate:

Dispatcher.BeginInvoke(delegate(List<JobViewModel> jobs)
{
    inbox.DataContext = jobs;
});

然而，能产生相同的编译时错误。

However, that yields the same compile-time error.

任何想法如何得到这个在WPF中工作？重构使用的BackgroundWorker 不是我的选择。

Any idea how to get this to work in WPF? Refactoring to use the BackgroundWorker is not an option for me.

推荐答案

您需要指定一个明确的委托类型。只需使用动作。

You need to specify an explicit delegate type. Just use an Action.

Dispatcher.BeginInvoke(new Action(() => populateInbox(args.Jobs));

您可以，但是，避免关闭在 args.Jobs 值是这样的：

You could, however, avoid having to close over the args.Jobs value like this:

Dispatcher.BeginInvoke(new Action((jobs) => populateInbox(jobs)), jobs);

这是因为 Dispatcher.BeginInvoke 的单参数版本的Silverlight中比在WPF不同的签名。在Silverlight中，它需要一个动作，这使得C＃编译器隐式键入您的拉姆达为动作。在WPF中，它需要一个代表（如Winforms中的 Control.BeginInvoke 模拟），所以C＃编译器必须已委托类型明确指定。

This is because the single-parameter version of Dispatcher.BeginInvoke has a different signature in Silverlight than in WPF. In Silverlight, it takes an Action, which allows the C# compiler to implicitly type your lambda as an Action. In WPF, it takes a Delegate (like its Control.BeginInvoke analog in Winforms), so the C# compiler has to have a delegate type explicitly specified.

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