在C#中使用鼠标点击在图片框上绘制线条

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

namespace DrawLineOnPictureBox
{
    public partial class Form1 : Form
    {
        private Point startPoint;
        private Point endPoint;

        public Form1()
        {
            InitializeComponent();
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            startPoint = e.Location;
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            endPoint = e.Location;
            pictureBox1.Invalidate(); // 触发PictureBox的重绘
        }

        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            if (startPoint != null && endPoint != null)
            {
                using (Pen pen = new Pen(Color.Red, 2))
                {
                    e.Graphics.DrawLine(pen, startPoint, endPoint);
                }
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            pictureBox1.BorderStyle = BorderStyle.FixedSingle;
        }
    }
}