title: How to draw multiple rectangles using c#
body: <p>I have drawn and saved the Rectangle on the image i loaded in the picture box. How i like to draw multiple rectangles for that i tried array in the rectangle but it gives error ("Object reference not set to an instance of an object." (Null reference Exception was unhandled).</p>
  
  <pre><code>private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
  {
      if (mybitmap == null)
      {
          mybitmap = new Bitmap(sz.Width, sz.Height);
      }
      rect[count] = new Rectangle(e.X, e.Y, 0, 0);
      this.Invalidate();
  }
  
  private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
  {
      if (stayToolStripMenuItem.Checked == true)
      {
          switch (e.Button)
          {
              case MouseButtons.Left:
              {
                  rect[count] = new Rectangle(rect[count].Left, rect[count].Top, e.X - rect[count].Left, e.Y - rect[count].Top);
                  pictureBox1.Invalidate();
                  count++:
                  break;
              }      
          }
      }
  }
  
  private void pictureBox1_Paint(object sender, PaintEventArgs e)
  {
      if (stayToolStripMenuItem.Checked == true)
      {
          button1.Visible = true;
          button2.Visible = true;
  
          if (mybitmap == null)
          {
              return;
          }
  
          using (g = Graphics.FromImage(mybitmap))
          {
              using (Pen pen = new Pen(Color.Red, 2))
              {
                  //g.Clear(Color.Transparent);
                  e.Graphics.DrawRectangle(pen, rect);
                  label1.Top = rect[count].Top; label1[count].Left = rect[count].Left; label1.Width = rect[count].Width;
                  label1.Height = rect[count].Height;
  
                  if (label1.TextAlign == ContentAlignment.TopLeft)
                  {
                      e.Graphics.DrawString(label1.Text, label1.Font, new SolidBrush(label1.ForeColor), rect);
                      g.DrawString(label1.Text, label1.Font, new SolidBrush(label1.ForeColor), rect);
                      g.DrawRectangle(pen, rect[count]);
                  }
              }
          }
      }
  }
  </code></pre>
  
  <p>How can i do this.....</p>