C#

musefan wrote:

So how would you 'inform' the form of a change?

public event EventHandler UCEvent;
protected virtual void OnUCEvent(EventArgs e)
{   
    EventHandler eh = UCEvent;
    if(eh != null)
        eh(this, e);
}

public partial class frmDetail : Form
    {
    // Signal file change happened
    public delegate void OnChangeHandler(object sender, EventArgs e);
    public static event OnChangeHandler OnChange;

    private void DoSomethingToChangeData()
       {
       OnChange(file, null);
       }
    }

public frmMain()
    {
    frmDetail.OnChange += new frmDetail.OnChangeHandler(OnChanged);
    }

private void ChangeCards()
    {
    // Let him see the detail.
    // Link in his event so if it cahnges, we detect it.
    frmDetail fd = new frmDetail(currentDetail);
    fd.ShowDialog();
    }

//
// Fired when the file is changed at a lower level.
//
private void OnChanged(object sender, EventArgs e)
    {
    FileChanged = true;
    }

protected virtual void OnChanged(EventArgs e)
{
    if(Changed != null)
        Changed(this, e);
}

// if using your own delegate use that instead of EventHandler
EventHandler eh = Changed;
if(eh != null)
    eh(this, e);

public partial class frmDetail : Form
    {
    // Signal file change happened
    public delegate void ChangeHandler(object sender, EventArgs e);
    public static event ChangeHandler Changed;

    protected virtual void OnChanged(EventArgs e)
       {
       ChangeHandler ch = Changed;
       if (ch != null)
          {
          ch(this, e);
          }
       }

    private void DoSomethingToChangeData()
       {
       OnChanged(null);
       }
    }

public frmMain()
    {
    frmDetail.Change += new frmDetail.ChangeHandler(Changed);
    }

private void ChangeCards()
    {
    // Let him see the detail.
    // Link in his event so if it cahnges, we detect it.
    frmDetail fd = new frmDetail(currentDetail);
    fd.ShowDialog();
    }

//
// Fired when the file is changed at a lower level.
//
private void Changed(object sender, EventArgs e)
    {
    FileChanged = true;
    }

fd = new frmDetails;
fd.Changed += ...

DaveyM69 wrote:

Static events are pretty dangerous, unless you explicitly unsubscribe from the event, the subscribing object will stay in memory even when you think it's gone as a reference is held to it in the delegate's invocation list!

Normally it's better to use instance ones, in which case you'd need a class level member variable
frmDetails fd;