c# - how to draw drawings in picture box

Question

draw pictures in picture Box on Mouse dragging using c#

Answer 1

Put a PictureBox on your form, and set its BackColor to White. Then add this code to your form (you have to actually hook up the Mouse events below, i.e. you can't just copy and paste this code into your form):

private Point? _Previous = null;
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
    _Previous = e.Location;
    pictureBox1_MouseMove(sender, e);
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if (_Previous != null)
    {
        if (pictureBox1.Image == null)
        {
            Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            using (Graphics g = Graphics.FromImage(bmp))
            {
                g.Clear(Color.White);
            }
            pictureBox1.Image = bmp;
        }
        using (Graphics g = Graphics.FromImage(pictureBox1.Image))
        {
            g.DrawLine(Pens.Black, _Previous.Value, e.Location);
        }
        pictureBox1.Invalidate();
        _Previous = e.Location;
    }
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
    _Previous = null;
}

And then draw away!

If you like, you can improve the quality of the drawn image somewhat by setting the Graphics object's SmoothingMode property.

Update: .Net CF does't have the Pens collection, and MoustEventArgs doesn't have a Location, so here is a CF-friendly version:

private Point? _Previous = null;
private Pen _Pen = new Pen(Color.Black);
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
    _Previous = new Point(e.X, e.Y);
    pictureBox1_MouseMove(sender, e);
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if (_Previous != null)
    {
        if (pictureBox1.Image == null)
        {
            Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            using (Graphics g = Graphics.FromImage(bmp))
            {
                g.Clear(Color.White);
            }
            pictureBox1.Image = bmp;
        }
        using (Graphics g = Graphics.FromImage(pictureBox1.Image))
        {
            g.DrawLine(_Pen, _Previous.Value.X, _Previous.Value.Y, e.X, e.Y);
        }
        pictureBox1.Invalidate();
        _Previous = new Point(e.X, e.Y);
    }
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
    _Previous = null;
}