Don't move the Labels outside a PictureBox

Question

I am creating an application in which I can move the Labels that are on a PictureBox.
The problem is that I want these to only Labels move inside the PictureBox.

Here is my code:

protected void lbl_MouseMove(object sender, MouseEventArgs e)
{
    Label lbl = sender as Label;

    try
    {
        if (lbl != null && e.Button == MouseButtons.Left)
        {
            if (m_lblLocation != new Point(0, 0))
            {
                Point newLocation = lbl.Location;
                newLocation.X = newLocation.X + e.X - m_lblLocation.X;
                newLocation.Y = newLocation.Y + e.Y - m_lblLocation.Y;
                lbl.Location = newLocation;
                this.Refresh();
            }
        }
    }
    catch(Exception ex) { }
}

protected void lbl_MouseUp(object sender, MouseEventArgs e)
{
    Label lbl = sender as Label;

    try
    {
        if (lbl != null && e.Button == MouseButtons.Left)
        {
            m_lblLocation = Point.Empty;
        }
    }
    catch(Exception ex) { }
}

protected void lbl_MouseDown(object sender, MouseEventArgs e)
{
    Label lbl = sender as Label;

    try
    {
        if (lbl != null && e.Button == MouseButtons.Left)
        {
            m_lblLocation = e.Location;
        }
    }
    catch(Exception ex) { }
}

In above code I have created some mouse events for the Labels.

Answer 1

you need to track two things: 1. is the mouse press or not - bool IsMouseDown = false; 2. the start location of the label- Point StartPoint;

// mouse is not down
private void label1_MouseUp(object sender, MouseEventArgs e)
{
    IsMouseDown = false;
}


 //mouse is down and set the starting postion
 private void label1_MouseDown(object sender, MouseEventArgs e)
 {   
     //if left mouse button was pressed
     if (e.Button == System.Windows.Forms.MouseButtons.Left)
     {
         IsMouseDown = true;
         label1.BringToFront();
         StartPoint = e.Location;
      }
   }


    //check the label is withing the borders of the picture box
    private void label1_MouseMove(object sender, MouseEventArgs e)
    {
        if (IsMouseDown)
        {
            int left = e.X + label1.Left - StartPoint.X;
            int right = e.X + label1.Right - StartPoint.X;
            int top = e.Y + label1.Top - StartPoint.Y;
            int bottom = e.Y + label1.Bottom - StartPoint.Y;
            if (left > pictureBox1.Left && top > pictureBox1.Top && pictureBox1.Bottom >= bottom && pictureBox1.Right >= right)
            {
                label1.Left = left;
                label1.Top = top;
            }
        }
    }