Dispatcher.BeginInvoke: Cannot convert lambda to System.Delegate

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?

Solution 1:

Shorter:

_dispatcher.BeginInvoke((Action)(() => DoSomething()));

Solution 2:

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));