Connection between 2 points with Draw method

[vanku]

Hello guys,
My problem is that when I want to draw 2 points on the form and connect them, the points do not appear but the connections are still on the form. I am using DrawEllipse and DrawLine methods.

 public partial class Form1 : Form
    {
        private Point p1, p2;
        List<Point> p1List = new List<Point>();
        List<Point> p2List = new List<Point>();
 
        public Form1()
        {
            InitializeComponent();
        }
 
        private void Form1_Paint(object sender, PaintEventArgs e)
        {
 
 
            using (var p = new Pen(Color.Blue, 4))
            {
                for (int x = 0; x < p1List.Count; x++)
                {
                    e.Graphics.DrawLine(p, p1List[x], p2List[x]);
                }
            }
 private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
 
            Graphics gr = this.CreateGraphics();
 
            int x = e.X;
            int y = e.Y;
 
            // Create pen.
            Pen whitePen = new Pen(Color.Blue, 3);
            Pen red = new Pen(Color.Red, 3);
            SolidBrush whiteBrush = new SolidBrush(Color.Blue);
 
            // Create rectangle for ellipse.
            Rectangle rect = new Rectangle(x - 5, y - 5, 10, 10);
 
            gr.DrawEllipse(whitePen, rect);
            gr.FillEllipse(whiteBrush, rect);
 
            if (p1.X == 0)
            {
                p1.X = e.X;
                p1.Y = e.Y;
            }
            else
            {
                p2.X = e.X;
                p2.Y = e.Y;
 
                p1List.Add(p1);
                p2List.Add(p2);
 
                Invalidate();
                p1.X = 0;
            }
         }
 
 
 
        }

On the first picture you can see my first click on the form it draws a point and on the second picture the connection is drawn but without the points.
I need your help please!