Dirt Simple C# .NET Custom Event for UserControl

Here’s my simple version

using System.ComponentModel;

    //Define a class to hold the event arguments, if one isn't already defined.
    public class DesignEventArgs : EventArgs
    {
        private DesignListItem item;

        public DesignEventArgs(DesignListItem item)
        {
            this.item = item;
        }

        public DesignListItem Item
        {
            get { return this.item; }
        }
    }

    //Create a delegate handler outside the user control class
    public delegate void SelectionChangedEventHandler(object sender, DesignEventArgs e);
    public partial class MySimpleUserControl : UserControl
    {
        //Declare the event using the delegate handler. Set a Browsable so it shows in the designer
        [Browsable(true)]
        public event SelectionChangedEventHandler SelectionChangedEvent;
        
        //Method that raises the event
        protected virtual void OnSelectionChangedEvent(DesignEventArgs e)
        {
            //Ensure the event is not null 
            SelectionChangedEventHandler sceh = this.SelectionChangedEvent;
            if (sceh !=null)
               sceh(this, e);
        }

        //Finally, the method which raises the event
        public void DoStuffToRaiseEvent()
        {
            //data for event args
            DesignListItem listItem = new DesignListItem();
            //build event args
            DesignEventArgs args = new DesignEventArgs(listItem);
            //Raise the event
            OnSelectionChangedEvent(args);
        }
    }

Now, over on the form… If your event is NOT displayed in the Designer’s Event List, you’ve done something wrong but this should register the event.

    //In the form constructor add:
    myUserControl.DesignChangedEvent += new DesignChangedEventHandler(myUserControl_DesignChangedEvent);

    //And add this method:
    protected void myUserControl_DesignChangedEvent(object sender, DesignEventArgs e)
    {
          //Do your stuff
    }