MethodInvoker vs Action for Control.BeginInvoke

Question

Which is more correct and why?

Control.BeginInvoke(new Action(DoSomething), null);

private void DoSomething()
    {
        MessageBox.Show("What a great post");
    }

or

Control.BeginInvoke((MethodInvoker)delegate { MessageBox.Show("What a great post"); });

I kinda feel like i am doing the same thing, so when is the right time to use MethodInvoker vs Action, or even writing a lamda?

edit: I know that really there isnt much of a difference between writing a lamda vs Action, but MethodInvoker seems to be made for a specific purpose. Is it doing anything different?

Answer 1

It is a matter of preference in most cases, unless you intend to reuse the DoSomething() method. Also the anonymous functions will place your scoped variables on the heap, might make it a more expensive function.

Answer 2

Also per MSDN:

MethodInvoker provides a simple delegate that is used to invoke a method with a void parameter list. This delegate can be used when making calls to a control's Invoke method, or when you need a simple delegate but do not want to define one yourself.

an Action on the other hand can take up to 4 parameters.

But I don't think there is any difference between MethodInvoker and Action as they both simply encapsulate a delegate that doesn't take a paremter and returns void

If you look at their definitions you'll simply see this.

public delegate void MethodInvoker();
public delegate void Action();

btw you could also write your second line as.

Control.BeginInvoke(new MethodInvoker(DoSomething), null);

Answer 3

Action is defined in System, while MethodInvoker is defined in System.Windows.Forms - you may be better off using Action, since it is portable to other places. You will also find more places that accept Action as a parameter than MethodInvoker.

However, the documentation does indicate that calls to delegates of type EventHandler or MethodInvoker in Control.Invoke() will be faster than any other type.

Aside from which namepsace they are in, I don't believe there is a meaningful functional difference between Action and MethodInvoker - they are essentially both defined as:

public delegate void NoParamMethod();

As an aside, Action has several overloads which allow parameters to be passed in - and it is generic so that they can be typesafe.

Answer 4

Both are equally correct, but the documentation for Control.Invoke states that:

The delegate can be an instance of EventHandler, in which case the sender parameter will contain this control, and the event parameter will contain EventArgs.Empty. The delegate can also be an instance of MethodInvoker, or any other delegate that takes a void parameter list. A call to an EventHandler or MethodInvoker delegate will be faster than a call to another type of delegate.

So MethodInvoker would be a more efficient choice.

Answer 5

I prefer using lambdas and Actions/Funcs:

Control.BeginInvoke(new Action(() => MessageBox.Show("What a great post")));