C#

using System;
using System.Collections;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Drawing;
using System.Data;
using System.Drawing.Drawing2D;
using System.Drawing.Design;
using System.Windows.Forms;
using System.Windows.Forms.Design;

namespace DeveloperNotes.LineControl
{
	public class LineControl : System.Windows.Forms.UserControl, ISupportInitialize
	{
		private Point start, end;
		private Color color;

		#region ISupportInitialize

		void ISupportInitialize.BeginInit() {}

		void ISupportInitialize.EndInit() {}

                  #endregion
		
		#region Properties
		[Category("Position"),Description("Starting position of line")]
		public Point Start
		{
			get{return start;}
			set{start = value;}
		}
		[Category("Position"),Description("Ending position of line")]
		public Point End
		{
			get{return end;}
			set{end = value;}
		}
		[Category("Line Color"),Description("Color of line")]
		public Color LineColor
		{
			get{return color;}
			set{color = value;}
		}
		#endregion

		#region Constructors
		public LineControl()
		{
			this.SetStyle(ControlStyles.DoubleBuffer, true);
			this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
			this.SetStyle(ControlStyles.ResizeRedraw, true);
		}
		public LineControl(int x1, int y1, int x2, int y2)
		{
			start.X = x1;
			start.Y = y1;
			end.X = x2;
			end.Y = y2;
		}
		public LineControl(Point pt1, Point pt2)
		{
			start = pt1;
			end = pt2;
		}
		#endregion

		#region Event Handlers

		protected override void OnPaint(PaintEventArgs pe) 
		{
			Graphics   g = pe.Graphics;
			SolidBrush brush = new SolidBrush(this.color);
			Pen pen = new Pen(brush, 1);
			Size       clientSize = this.ClientRectangle.Size;
			g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
			g.DrawLine(pen, this.start, this.end);
			base.OnPaint(pe);
		}
		#endregion

	}
}

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