用于突出显示鼠标选择区域的c#绘图方块

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

public class MainForm : Form
{
    private Point startPoint;
    private Point endPoint;
    private bool isDrawing;

    public MainForm()
    {
        // 初始化窗体和相关事件
        this.Paint += new PaintEventHandler(MainForm_Paint);
        this.MouseDown += new MouseEventHandler(MainForm_MouseDown);
        this.MouseUp += new MouseEventHandler(MainForm_MouseUp);
    }

    private void MainForm_Paint(object sender, PaintEventArgs e)
    {
        if (isDrawing)
        {
            // 绘制矩形
            int x = Math.Min(startPoint.X, endPoint.X);
            int y = Math.Min(startPoint.Y, endPoint.Y);
            int width = Math.Abs(startPoint.X - endPoint.X);
            int height = Math.Abs(startPoint.Y - endPoint.Y);
            Rectangle rect = new Rectangle(x, y, width, height);
            Pen pen = new Pen(Color.Red, 2);
            e.Graphics.DrawRectangle(pen, rect);
        }
    }

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

    private void MainForm_MouseUp(object sender, MouseEventArgs e)
    {
        endPoint = e.Location;
        isDrawing = false;
        this.Invalidate(); // 刷新窗体，触发Paint事件
    }

    public static void Main()
    {
        Application.Run(new MainForm());
    }
}