Listening to Events in Main Form from Another Form in C#

Question

I have an application that has a main form and uses an event handler to process incoming data and reflect the changes in various controls on the main form. This works fine.

Answer 1

Consider using loosely coupled events. This will allow you to couple the classes in such a way that they never have to be directly aware of each other. The Unity application block comes with an extension called EventBroker that makes this very simple.

Here's a little lick of the sugar:

public static class EVENTS
{
    public const string UPDATE_TICKED = "event://Form1/Ticked";
}

public partial class Form1 : Form
{
    [Publishes(EVENTS.UPDATE_TICKED)]
    public event EventHandler Ticked; 

    void the_timer_Tick(object sender, EventArgs e)
    {
        // I would like code in here to update all instances of SecondaryForm
        // that happen to be open now.
        MessageBox.Show("Timer ticked");
        OnTicked();
    }

    protected virtual void OnTicked()
    {
        if (Ticked == null) return;
        Ticked(this, e);
    }
}

public partial class SecondaryForm : Form
{
    [SubscribesTo(EVENTS.UPDATE_TICKED)]
    private void Form1_Ticked(object sender, EventHandler e)
    {
        // code to handle tick in SecondaryForm
    }
}

Now if you construct both of these classes using Unity, they will automatically be wired together.

Update

Newer solutions use message bus to handle loosely coupled events. See http://masstransit-project.com/ or http://nimbusapi.github.io/ as examples.