如何在C#中创建图形上的圆和线？

using System;
using System.Drawing;
using System.Windows.Forms;

public class CircleForm : Form
{
    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        
        Graphics g = e.Graphics;
        Pen pen = new Pen(Color.Black, 2);
        Rectangle rect = new Rectangle(50, 50, 100, 100);
        
        g.DrawEllipse(pen, rect);
    }
    
    public static void Main()
    {
        Application.Run(new CircleForm());
    }
}

using System;
using System.Drawing;
using System.Windows.Forms;

public class LineForm : Form
{
    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        
        Graphics g = e.Graphics;
        Pen pen = new Pen(Color.Black, 2);
        Point startPoint = new Point(50, 50);
        Point endPoint = new Point(150, 150);
        
        g.DrawLine(pen, startPoint, endPoint);
    }
    
    public static void Main()
    {
        Application.Run(new LineForm());
    }
}