Закрепление дочерней формы к родительской

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsApplication3 {
    public partial class MainForm : Form {
        public static event EventHandler LocationEvent = delegate { };
        public MainForm() {
            InitializeComponent();
            this.LocationChanged += new EventHandler(MainForm_LocationChanged);
            btnShowSecondForm.Click += new EventHandler(btnShowSecondForm_Click);
        }
 
        void MainForm_LocationChanged(object sender, EventArgs e) {
            LocationEvent(this, EventArgs.Empty);
        }
 
        
        void btnShowSecondForm_Click(object sender, EventArgs e) {
            SecondForm second = new SecondForm();
            second.StartPosition = FormStartPosition.Manual;
            second.Location = this.Location + 
                SystemInformation.CaptionButtonSize + 
                SystemInformation.FrameBorderSize;
            second.Show();
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsApplication3 {
    public partial class SecondForm : Form {
        public SecondForm() {
            InitializeComponent();
            MainForm.LocationEvent += new EventHandler(MainForm_LocationEvent);
        }
 
        void MainForm_LocationEvent(object sender, EventArgs e) {
            MainForm mf = sender as MainForm;
            this.Location = mf.Location + 
                SystemInformation.CaptionButtonSize +
                SystemInformation.FrameBorderSize;
        }
    }
}