Erase lines over Image in PictureBox which were drawn on Mouse Click

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C#

Hello friends,,

I am working on drawing Lines using (DrawLines) over Image in picturebox,I am able to draw lines using below code,,But i want when user click on Button (provided below picture box) all the lines which user have drawn over the image should be Erased .

Thanks,,,,,

private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
        {
                 
 
            pointArray[iNumberofClicks].X = e.X;
            pointArray[iNumberofClicks].Y = e.Y;
            Pen PenSpikes = new Pen(Color.Green);
            SolidBrush solidBrush = new SolidBrush(Color.Blue);
 
            if(iNumberofClicks==0)
            {
                 a = e.X;
                 b = e.Y;
            }
 
            iNumberofClicks++;
            if (iNumberofClicks > 1)
            {
                Point[] CurrentpointArray = new Point[iNumberofClicks];
 
                for (int aa = 0; aa < iNumberofClicks; aa++)
                {
                    CurrentpointArray[aa].X = pointArray[aa].X;
                    CurrentpointArray[aa].Y = pointArray[aa].Y;
 
                }
 
               
               Graphics offScreenDC = Graphics.FromImage(pictureBox1.Image);
                offScreenDC.DrawLines(PenSpikes, CurrentpointArray);
                offScreenDC.Dispose();
                pictureBox1.Refresh();
                
               
}
}
for (int j = 1; j < CurrentpointArray.Length;j++ )
              {
                  if ((Convert.ToInt16(CurrentpointArray[j].X) == a && Convert.ToInt16(CurrentpointArray[j].Y) == b) )
                  {
                      MessageBox.Show("alert");
                      break;
                  }
              }