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

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        
        Rectangle rcx = new Rectangle(0,0,0,0);
        Boolean lstart = false;       
        Point lct;
        Point imgs;

        private void Form1_Load(object sender, EventArgs e)
        {                       
            pictureBox1.Image = new Bitmap("C:/test.bmp");
            imgs.X = pictureBox1.Image.Width;
            imgs.Y = pictureBox1.Image.Height;
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {           
            lstart = true;
            lct = e.Location;
            Point startPoint = pictureBox1.PointToScreen(new Point(e.X, e.Y));
            rcx.X = startPoint.X;
            rcx.Y = startPoint.Y;
        }

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            this.Text = e.X + " : " + e.Y;

            if (lstart)
            {
                Point endPoint = pictureBox1.PointToScreen(new Point(e.X, e.Y));

                if (e.X > -1 && e.X <= imgs.X && e.Y > -1 && e.Y <= imgs.Y)
                {
                    rcx.Height = endPoint.Y - rcx.Y - 1;
                    rcx.Width = endPoint.X - rcx.X - 1;

                    this.Refresh();
                    ControlPaint.DrawReversibleFrame(rcx, this.BackColor, FrameStyle.Dashed);
                }
            }
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            lstart = false;
            Point endPoint = e.Location;
            if (endPoint.X < 0) endPoint.X = 0;
            if (endPoint.Y < 0) endPoint.Y = 0;

            richTextBox1.Text = "x1:" + lct.X.ToString() + "\n" + "y1:" + lct.Y.ToString() + "\n" +
                "x2:" + endPoint.X.ToString() + "\n" + "y2:" + endPoint.Y.ToString();
           
            //rcx = new Rectangle(0, 0, 0, 0);
        }
    }
}

 

örnek görünüm:

Abi bende asp.net ile ilgili bi keşim peşindeyim.Eğer aklımdakini yapabilirsem çok güzel bi uygulama olucak.