C# 선택영역 점선 표시

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        // The following three methods will draw a rectangle and allow 
        // the user to use the mouse to resize the rectangle.  If the 
        // rectangle intersects a control's client rectangle, the 
        // control's color will change.

        bool isDrag = false;
        Rectangle theRectangle = new Rectangle
            (new Point(0, 0), new Size(0, 0));
        Point startPoint;

        private void Form1_MouseDown(object sender,
            System.Windows.Forms.MouseEventArgs e)
        {

            // Set the isDrag variable to true and get the starting point 
            // by using the PointToScreen method to convert form 
            // coordinates to screen coordinates.
            if (e.Button == MouseButtons.Left)
            {
                isDrag = true;
            }

            Control control = (Control)sender;

            // Calculate the startPoint by using the PointToScreen 
            // method.
            startPoint = control.PointToScreen(new Point(e.X, e.Y));
        }

        private void Form1_MouseMove(object sender,
            System.Windows.Forms.MouseEventArgs e)
        {

            // If the mouse is being dragged, 
            // undraw and redraw the rectangle as the mouse moves.
            if (isDrag)

            // Hide the previous rectangle by calling the 
            // DrawReversibleFrame method with the same parameters.
            {
                ControlPaint.DrawReversibleFrame(theRectangle,
                    this.BackColor, FrameStyle.Dashed);

                // Calculate the endpoint and dimensions for the new 
                // rectangle, again using the PointToScreen method.
                Point endPoint = ((Control)sender).PointToScreen(new Point(e.X, e.Y));

                int width = endPoint.X - startPoint.X;
                int height = endPoint.Y - startPoint.Y;
                theRectangle = new Rectangle(startPoint.X,
                    startPoint.Y, width, height);

                // Draw the new rectangle by calling DrawReversibleFrame
                // again.  
                ControlPaint.DrawReversibleFrame(theRectangle,
                    this.BackColor, FrameStyle.Dashed);
            }
        }

        private void Form1_MouseUp(object sender,
            System.Windows.Forms.MouseEventArgs e)
        {

            // If the MouseUp event occurs, the user is not dragging.
            isDrag = false;

            // Draw the rectangle to be evaluated. Set a dashed frame style 
            // using the FrameStyle enumeration.
            ControlPaint.DrawReversibleFrame(theRectangle,
                this.BackColor, FrameStyle.Dashed);

            // Find out which controls intersect the rectangle and 
            // change their color. The method uses the RectangleToScreen  
            // method to convert the Control's client coordinates 
            // to screen coordinates.
            Rectangle controlRectangle;
            for (int i = 0; i < Controls.Count; i++)
            {
                controlRectangle = Controls[i].RectangleToScreen(Controls[i].ClientRectangle);
                if (controlRectangle.IntersectsWith(theRectangle))
                {
                    Controls[i].BackColor = Color.BurlyWood;
                }
            }

            // Reset the rectangle.
            theRectangle = new Rectangle(0, 0, 0, 0);
        }



    }