Question

I have gotten a bit lazy(it’s sometimes good) and started updating WinForms UI by invoking a callback without checking InvokeRequired first.

Are there a performance issues or considerations that I should be aware of?

    private delegate void SetStatusEventHandler(string statusMessage);     private void SetStatus(string statusMessage)     {         Invoke((MethodInvoker) (() =>         {             resultLabel.Text = statusMessage;         }));          //  - vs -          if (InvokeRequired)         {             SetStatusEventHandler cb = SetStatus;             Invoke(cb, statusMessage);         }         else         {             resultLabel.Text = statusMessage;         }     } 

[EDIT]: Most of times that a method that calls ‘invoke’ will be called at most like say 10~20 times a second with a wide interval inbetween.

[UPDATE] Settled with the following extension method

public static class SmartInvoker {     public static void InvokeHandler(this Control control, MethodInvoker del)     {         if (control.InvokeRequired)         {             control.Invoke(del);             return;         }         del();     } }  ...      private void SetStatus(string statusMessage)     {         this.InvokeHandler(() => resultLabel.Text = statusMessage);     } 

I guess finding out how to manage extension method classes is another topic I need to dig in. Thank you for your help

Answer 1

EDIT: See the comments for debate about the whole posting vs immediately dispatching malarky.

Either way, my answer is actually the same: unless this is happening hugely often unnecessarily (i.e. most of the time you’re on the UI thread to start with, and it’s attached to something like a mouse movement handler) I wouldn’t worry. It certainly makes the code simpler. If this is going to be invoked very often, I’d measure and test more 🙂

Invoke is faster with an EventHandler or MethodInvoker delegate than with others. I don’t know if there’s any difference between the two – you may want to check.

You can make this even simpler by writing an extension method, e.g.

public static void InvokeHandler(this Control control, MethodInvoker handler) {      control.Invoke(handler); } 

Then you can make your code:

private void SetStatus(string statusMessage) {     this.InvokeHandler(delegate     {         resultLabel.Text = statusMessage;     }); } 

or

private void SetStatus(string statusMessage) {     InvokeHandler(() => resultLabel.Text = statusMessage); } 

That way you don’t need to specify the delegate type.