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An Action (callback) with parameters and return value

Posted on 2013-11-14
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Last Modified: 2013-11-14
Hi Experts,

How would I go about creating/using an Action (callback) with parameters and return value.

So here's what I am trying to accomplish:

I have a UI exe and a DLL that performs syncing operations in a background thread.  Every now and again the syncing thread needs input from the user.  What I am thinking about doing, is when the UI instantiates the background thread, it would pass it a function pointer/Action (pointing to one of the UI’s functions that would pop up a message box for the user).  Then from that point on, any time the syncing thread needs to interact with the user, it’ll use this callback function to interact with the user.  The user would click Yes/No and then that would be returned to the thread and the read would zig or zag based on the user’s input.  How would the Action declaration look like for this and how would the class constructor (accepting the function pointer) look like?

I am thinking something like this but I know I’m missing the return value:

(Please ignore the simplification of the thread part)

public class SyncerClass
{
     private Action<MyParameterClass> _useMessageCallback;

     public SyncerClass(Action<MyParameterClass> useMessageCallback)
     {
          _useMessageCallback = useMessageCallback;
          Thread.StartThread(WorkerThread);
     }

     WorkerThread()
     {
      while(true)
      {
                         MyParameterClass parameter = new MyParameterClass();
                         arameter.Message = “Would you like me to Zig instead of Zag?”;

                         if(_useMessageCallback(parameter) == DialogResult.Yes)
                         {
                              //Zig
                         }
                         else
                         {
                              //Zag
                         }
               }
     }
}

Thank you!
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Question by:axnst2
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6 Comments
 
LVL 22

Accepted Solution

by:
p_davis earned 2000 total points
ID: 39648374
if you want a result you would either have to use func<T, TResult> or a delegate... i would suggest a delegate
0
 

Author Comment

by:axnst2
ID: 39648423
With func it worked!  Thanks!

Why would you prefer the delegate and what would the delegate prototype look like?
0
 

Author Comment

by:axnst2
ID: 39648428
delegate TResult MyDelegate(T)?
0
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LVL 22

Expert Comment

by:p_davis
ID: 39648451
Its just a preference of mine... if func suites you, use it.
0
 
LVL 22

Expert Comment

by:p_davis
ID: 39648457
func actually is a delegate too, anyway
0
 

Author Closing Comment

by:axnst2
ID: 39648548
Thank you!

I ended up using this:

Func<UIMessageParameters, DialogResult> _displayUserMessage;
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