Question

NET programming.I have a image of a map with latitudes and longitudes on its borders .now when i drag the mouse on the map i should get a rectangle with one vertex at the mouse point and opposite one at the top left corner of map ,so that i can exactly pin pointedly locate the pixel with latitude and longitude.to be clear it should appear as a rectangle when we drag mouse on the screen.I have a code which is partially working

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        // "e.X" and "e.Y" are used to get MousePositionX and MousePositionY
        rect = new Rectangle(e.X, e.Y, 0, 0);
        this.Invalidate();
    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        // This makes sure that the left mouse button is pressed.
        if (e.Button == MouseButtons.Left)
        {
            // Draws the rectangle as the mouse moves
            rect = new Rectangle(rect.Left, rect.Top, e.X - rect.Left, e.Y - rect.Top);
        }
        this.Invalidate();
    }

    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {

        using (Pen pen = new Pen(Color.Red, 2))
        {
            e.Graphics.DrawRectangle(pen, rect);
        }
    }

I don’t know where the problem exactly is but could draw a rectangle at run time.any one please help me with changes in the code.

Answer 1

tafa’s Answer works.

I only got two additions:

1. In the MouseDown Method you should
   also use the following code. So
   once you click somewhere in the map
   you get a rectangle even when not
   moving the mouse.

   rect = new Rectangle(0, 0, e.X, e.Y);
   

2. In the MouseMove method I would use the following code, to not create new Rectangles whenever you move the mouse:

   rect.Width = e.X;  
   rect.Height = e.Y;