Events between many forms - Publisher/Subscriber

[loliloli]

I want to define message, which a set of forms to listen for it, and each of them to raise.
For example:
BaseForm:Form{
publuc event EventHandler DataChanged;
protected virtual void OnDataChanged
{
if(DataChanged != null)
DataChanged(this, new EventHandler());
}
ChildForm:BaseForm
listen for the message
SecondForm:BaseForm
listen for the message and raise message

What is the schema for this. Something like SendMessage, PostMessage and WinProc in C APIs
Any Ideas!

 

[Qik3Coder]

The complexity depends on how much data you are trying to send back and forth.

This is what is known as the "Observer Pattern". You will need to keep a listing of all of the forms/class instances that need to be notified when X happens.

Start writing code and when you get stuck post code bits.

Lodlaiden

A lack of experience doesn't prevent you from doing a good job.

 

[loliloli]

Thanks you for the reply!
I read for this model and make a small project to test it. It's seem to work but I used static array in the base class of the forms. It's not very good idea, I think. Some other idea to avoid this.

 

[jmeckley]

I like to handle this scenario using the concept of an event broker. this way the individual UI components are not dependent on one another.

I put together a simple broker using Castle Windsor.

http://docs.castleproject.org/Windsor.Extensibility_Sample_App_EventBrokerFacility.ashx.

The primary focus was extending castle Windsor more than the event broker, but the idea is there. source is hosted on github.

an example of what a form or user component might look like

class ThisUserControl 
   : UserControl
{
   private readonly IEventBroker broker;

   public MyForm(IEventBroker broker)
   {
       this.broker = broker;
   }

   private void MyForm_ButtonClick(object sender, EventArgs e)
   {
       var message = new DoSomethingImportant
                          {
                             Text = "...", 
                             Date = DatePicker.SelectedDate, 
                             Number = int.Parse(Spinner.Value)
                          };
       broker.send(message);
   }
}

public class ThatUserControl 
   : UserControl
     , IListener<ImportantMessage>
{
   public void Handle(ImportantMessage message)
   {
        use message to update this user control.
   }
}

code for the event broker & castle windsor:

https://github.com/kkozmic/Castle.Samples.Extensibility

Jason Meckley
Programmer

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