WPF "DoEvents": how to implement it?

Question

I found this two implementation for "DoEvents" method:

SOLUTION 1:

System.Windows.Application.Current.Dispatcher.Invoke(
       System.Windows.Threading.DispatcherPriority.Background,
       new System.Threading.ThreadStart(() => { }));

SOLUTION 2:

System.Windows.Application.Current.Dispatcher.Invoke(
       System.Windows.Threading.DispatcherPriority.Background,
       new System.Action(delegate { }));

Could you explain what is the difference between these two implementations, and what is the most appropriate to use?

Thanks.

Why do you think you need this? DoEvents is ugly in WinForms as well. — JeffRSon, Nov 07 '14 at 10:15
Yes, I know, but I have a situation where there is a running BackgroundWorker and I should put on hold until it is "busy". In any case, what is the difference between the two implementations that I quoted? — Luca Petrini, Nov 07 '14 at 10:21
There's no practical difference, just the type of delegate. IMO, solution 2 is better readable. — JeffRSon, Nov 07 '14 at 10:43
Don't use a `DoEvents`-style method if you can avoid it (hint: you can avoid it). Use an event handler or some kind of continuation mechanism (e.g., `async/await`) to resume execution. Busy-waiting is just going to drive up your CPU usage. — Mike Strobel, Nov 07 '14 at 20:12

score 1 · Answer 1 · edited May 23 '17 at 10:25

They both are delegates,when your event execution needs to done it will initiate the events when your criteria met (e.g, Here in case when execution reached and dispatcher priority background reached) They are just two different implementation ways you can refer

What is the difference between Delegate & Action in C#

or msdn for information

http://msdn.microsoft.com/en-us/library/system.threading.threadstart(v=vs.110).aspx

http://msdn.microsoft.com/en-us/library/system.action(v=vs.110).aspx

score 1 · Accepted Answer · answered Nov 07 '14 at 10:44

There is no difference between both solutions except the syntax. ThreadStart and Action are both delegates which have the same declaration and only a name is different:

public delegate void ThreadStart();
public delegate void Action();

You can also create your own delegate and use is in the same way e.g.:

public delegate void MyOwnAction();
...
Application.Current.Dispatcher.Invoke(
    DispatcherPriority.Background, new MyOwnAction(() => { }));

You can also use a specific method and not anonymous one:

private void Target()
{
    ...
}

Application.Current.Dispatcher.Invoke(
    DispatcherPriority.Background, new MyOwnAction(Target));

WPF "DoEvents": how to implement it?

2 Answers2