Click two new points and draw a line between those two points using mouse event

Hi Ryan Madlangbayan,
Following is your code, Please mark my answer as accepted if it helped you:

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 WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Point p1, p2;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            if (p1.X == 0)
            {
                p1.X = e.X;
                p1.Y = e.Y;

            }
            else
            {
                p2.X = e.X;
                p2.Y = e.Y;
                Graphics graph = this.CreateGraphics();
                Pen penCurrent = new Pen(Color.Red, 3);
                graph.DrawLine(penCurrent, p1, p2);
            }
        }
    }
}