具有匿名委托的Dispatcher.Invoke适用于Silverlight但不适用于WPF

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:

在Silverlight 4中，我有一个自定义服务类，它具有异步的Completed事件。在Completed事件中，我获取返回的数据并通过以下方式调用populate方法：

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

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

The BeginInvoke works in SL4, however when I ported it to WPF I get the following error:

BeginInvoke在SL4中工作，但是当我将它移植到WPF时，我收到以下错误：

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

无法将lambda表达式转换为类型'System.Delegate'，因为它不是委托类型

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

我尝试将其更改为内联，匿名，参与代表：

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

However, that yields the same compile-time error.

但是，这会产生相同的编译时错误。

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

知道如何在WPF中使用它吗？重构使用BackgroundWorker对我来说不是一个选择。

2 个解决方案

#1

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

您需要指定显式委托类型。只需使用动作即可。

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

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

但是，您可以避免必须关闭args.Jobs值，如下所示：

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

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.

这是因为Dispatcher.BeginInvoke的单参数版本在Silverlight中具有与WPF中不同的签名。在Silverlight中，它采用一个Action，它允许C＃编译器隐式地将lambda键入为Action。在WPF中，它需要一个Delegate（就像它在Winforms中的Control.BeginInvoke模拟一样），因此C＃编译器必须明确指定一个委托类型。

#2

In WPF and winforms you must cast it to a MethodInvoker first, otherwise you will get the error Cannot convert anonymous method to type 'System.Delegate' because it is not a delegate type.

在WPF和winforms中，您必须首先将它转换为MethodInvoker，否则您将收到错误无法将匿名方法转换为类型'System.Delegate'，因为它不是委托类型。

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

For more info: http://msdn.microsoft.com/en-us/library/system.windows.forms.methodinvoker.aspx

有关详细信息：http：//msdn.microsoft.com/en-us/library/system.windows.forms.methodinvoker.aspx

#1