问题
I'm trying to call System.Windows.Threading.Dispatcher.BeginInvoke
. The signature of the method is this:
BeginInvoke(Delegate method, params object[] args)
I'm trying to pass it a Lambda instead of having to create a Delegate.
_dispatcher.BeginInvoke((sender) => { DoSomething(); }, new object[] { this } );
It's giving me a compiler error saying that I
can't convert the lambda to a System.Delegate.
The signature of the delegate takes an object as a parameter and returns void. My lambda matches this, yet it's not working. What am I missing?
回答1:
Since the method takes a System.Delegate, you need to give it a specific type of delegate, declared as such. This can be done via a cast or a creation of the specified delegate via new DelegateType as follows:
_dispatcher.BeginInvoke(
new Action<MyClass>((sender) => { DoSomething(); }),
new object[] { this }
);
Also, as SLaks points out, Dispatcher.BeginInvoke takes a params array, so you can just write:
_dispatcher.BeginInvoke(
new Action<MyClass>((sender) => { DoSomething(); }),
this
);
Or, if DoSomething is a method on this object itself:
_dispatcher.BeginInvoke(new Action(this.DoSomething));
回答2:
Shorter:
_dispatcher.BeginInvoke((Action)(() => DoSomething()));
回答3:
Using Inline Lambda...
Dispatcher.BeginInvoke((Action)(()=>{
//Write Code Here
}));
回答4:
If you reference System.Windows.Presentation.dll from your project and add using System.Windows.Threading
then you can access an extension method that allows you to use the lambda syntax.
using System.Windows.Threading;
...
Dispatcher.BeginInvoke(() =>
{
});
回答5:
We create extension methods for this. E.g.
public static void BeginInvoke(this Control control, Action action)
=> control.BeginInvoke(action);
Now we can call it from within a form: this.BeginInvoke(() => { ... })
.
来源:https://stackoverflow.com/questions/4936459/dispatcher-begininvoke-cannot-convert-lambda-to-system-delegate