Line wont show up

[qutspan]

When I create taskbox on the form the line beside the box wont show up.
it show up untill I have MouseEnter event occur.
Also when I have 2 taskbox on the form it does draw the line around the label
however the line wont draw when i have 1 taskbox move away from another taskbox. The line is gone at last sec when taskbox move away.

could someone please tell me where does I made mistake and how to fix it
thank you
Below is the code.

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
 
namespace Task
{
    public class TaskBox: Label
    {
        private bool m_IsPressed;
        private int curDifX,curDifY;
        private const int STEPBOX_WIDTH = 105;
        private const int STEPBOX_HEIGHT = 25;
 
        public event MouseRightKeyPressHandler MouseRightKeyPress;
        public delegate void MouseRightKeyPressHandler(object sender, MouseEventArgs e);
 
        public event DeleteTaskHandler DeleteTask;
        public delegate void DeleteTaskHandler(object sender);
 
 
        public TaskBox(string name) {
 
            this.Text = name;
            this.TextAlign = ContentAlignment.MiddleCenter;
            this.BorderStyle = BorderStyle.None;
            this.Size = new Size(STEPBOX_WIDTH, STEPBOX_HEIGHT);
            this.MouseDown += new System.Windows.Forms.MouseEventHandler(this_MouseDown);
            this.MouseMove += new System.Windows.Forms.MouseEventHandler(this_MouseMove);
            this.KeyUp += new System.Windows.Forms.KeyEventHandler(this_KeyUp);
            this.MouseUp += new System.Windows.Forms.MouseEventHandler(this_MouseUp);
            this.MouseLeave += new EventHandler(this_MouseLeave);
            this.MouseEnter += new EventHandler(this_MouseEnter);
            this.BackColor = Color.FromKnownColor(KnownColor.Control);
            this.LostFocus+=new EventHandler(this_LostFocus);
            this.Paint+=new PaintEventHandler(TaskBox_Paint);
 
       }
 
          private void this_MouseDown(object sender, MouseEventArgs e)
        {
            m_IsPressed = true;
            (sender as TaskBox).Select();
            curDifX = Cursor.Position.X - (sender as Label).Left;
            curDifY = Cursor.Position.Y - (sender as Label).Top;
            (sender as TaskBox).BackColor = Color.Teal;
            if (e.Button == MouseButtons.Right)
            {
                if (MouseRightKeyPress != null)
                {
 
                    MouseRightKeyPress(this, e);
                }
            }
 
        }
 
        private void this_MouseMove(object sender, MouseEventArgs e)
        {
            if (m_IsPressed == true)
            {
                if (Cursor.Position.X - curDifX < 0)
                {
                    (sender as TaskBox).Left = 0;
                }
                else
                {
                    (sender as TaskBox).Left = Cursor.Position.X - curDifX;
                }
 
                if (Cursor.Position.Y - curDifY < 0)
                {
                    (sender as TaskBox).Top = 0;
 
                }
                else
                {
                    (sender as TaskBox).Top = Cursor.Position.Y - curDifY;
                }
 
                (sender as TaskBox).BringToFront();
 
            }
        }
 
        private void this_MouseUp(object sender, MouseEventArgs e)
        {
            (sender as TaskBox).BackColor = Color.Teal;
            m_IsPressed = false;
 
        }
 
         private void this_MouseEnter(object sender, EventArgs e)
        {
            Graphics g = (sender as TaskBox).CreateGraphics();
            g.DrawRectangle(Pens.Red, 0, 0, STEPBOX_WIDTH-1, STEPBOX_HEIGHT-1);
        }
        private void this_MouseLeave(object sender, EventArgs e)
        {
            Graphics g = (sender as TaskBox).CreateGraphics();
            g.DrawRectangle(Pens.Black, 0, 0, STEPBOX_WIDTH-1, STEPBOX_HEIGHT-1);
        }
 
        private void this_KeyUp(object sender, KeyEventArgs e)
        {
            if (e.KeyData == Keys.Delete)
            {
                DeleteTask(this);
            }
        }
 
 
        public void TaskBox_Paint(Object sender,PaintEventArgs e)
        {
            Graphics g = (sender as TaskBox).CreateGraphics();
 
 
            if (m_IsPressed)
            {
                g.DrawRectangle(Pens.Red, 0, 0, STEPBOX_WIDTH - 1, STEPBOX_HEIGHT - 1);
            }
            else
            {
                g.DrawRectangle(Pens.Black, 0, 0, STEPBOX_WIDTH - 1, STEPBOX_HEIGHT - 1);
            }
 
        }
 
        private void this_LostFocus(object sender, EventArgs e)
        {
 
            (sender as TaskBox).BackColor = Color.FromKnownColor(KnownColor.Control);
        }
 
    }
}