C#

using System.Windows.Forms;
using System.Drawing;

namespace MyControls
{
    public class ImageTextBox : TextBox
    {
        private Image image;
        public Image Image
        {
            get { return image; }
            set
            {
                image = value;
                //Do other stuff here
            }
        }
    }
}

[CategoryAttribute("Harveys Events")]
[DescriptionAttribute("Happens when I want it!")]		
public event EventHandler HarveysParentEvent;

public class MDIBaseChild : System.Windows.Forms.Form

public class MDIChild1 : MDIBaseChild

private MDIParent mdiParent=null; //holds the reference to the parent form
 
protected override void OnParentChanged(EventArgs e)
{
    //MDIChild is added to the MDIParent
    if(Parent!=null)
    {
        if(mdiParent==null)
        {
            if(Parent is MdiClient)
            {
                mdiParent = Parent.TopLevelControl as MDIParent;
                if(mdiParent!=null)
                {
                    //Handles the event
                    mdiParent.HarveysParentEvent+=new EventHandler(mdiParent_HarveysParentEvent);
                }
            }
        }
    }
    //MDIChild has Closed and/or was removed from MDIParent
    else
    {
        if(mdiParent!=null)
        {
            //clears the reference to the parent Form
            mdiParent.Activated-=new EventHandler(mdiParent_HarveysParentEvent);
            mdiParent.HarveysParentEvent-=new EventHandler(mdiParent_HarveysParentEvent); //Edited
            mdiParent = null;
        }
    }
 
    base.OnParentChanged (e);
}

//Base Child code
protected virtual void mdiParent_HarveysParentEvent(object sender, EventArgs e)
{
}
 
//Inherited Child code
protected override void mdiParent_HarveysParentEvent(object sender, EventArgs e)
{
    //Implement your code here
 
    base.mdiParent_HarveysParentEvent(sender, e);
}

//client MainForm code
//message from server
    if(HarveysParentEvent!=null)
    {
        HarveysParentEvent(this, EventArgs.Empty);
    }

HarveySaayman wrote:

(remember some are dialog windows)

public partial class Form1 : Form
    {
        public event EventHandler MyEvent;

        public Form1()
        {
            InitializeComponent();
            this.IsMdiContainer = true;

            ChildForm f = new ChildForm(this);
            f.MdiParent = this;
            f.Size = new Size(100, 100);
            f.Text = "Child form";
            f.BackColor = Color.Black;
            f.Show();

            this.SizeChanged += new EventHandler(Form1_SizeChanged);
        }

        void Form1_SizeChanged(object sender, EventArgs e)
        {
            if (MyEvent != null)
                MyEvent(this, EventArgs.Empty);      
        }

    }

public partial class ChildForm : Form
    {
        public ChildForm(Form1 f)
        {
            f.MyEvent += new EventHandler(f_MyEvent);
            InitializeComponent();
        }

        void f_MyEvent(object sender, EventArgs e)
        {
            Thread.Sleep(1000);
            this.Close();
        }
    }