Events in UserControl

Question

Hi all, I am new to UserControls, and while developing my own control I found a problem with showing events of my control in the property grid at design time. If I have some events in my control I want to see them in Property grid and if I double-click that I want to have a handler, in the same way Microsoft does for its controls.

Answer 1

They should automatically appear if I'm not mistaken. Make sure you've built your project though, or changes won't propagate to open designers. And make sure it's a public event too. (Private/protected events rightfully shouldn't show up because they're not accessible.)

One thing you can do to make your user's design experience nicer is to do something like the following:

    [Description("This event is raised when the user presses the enter key while the control has focus."),
    Category("Key")]
    public event EventHandler EnterPressed;

The "description" bit puts a nice message in the description panel of the property window. The "category" bit puts it in a certain category (the default is Misc. at the end).

By the way, you haven't specified a language or environment, so the above may need to be modified if it's not C# in Visual Studio 2005+.

Answer 2

I usually use this pattern, to create a custom event in UserControls:

    #region MyEvent CUSTOM EVENT

    protected virtual void OnMyEvent(MyEventEventArgs e)
    {
        if (MyEvent != null)
            MyEvent(this, e);
    }

    public delegate void MyEventHandler(object sender, MyEventEventArgs e);
    public event MyEventHandler MyEvent;

    public class MyEventEventArgs : EventArgs
    {

    }

    #endregion MyEvent CUSTOM EVENT

This has the same naming convention of Microsoft events, you can fire OnMyEvent from inside your control, have custom EventArgs, handle MyEvent from other controls.