Parameter is not valid. when using 'for loop'

Question

I am converting system.byte[] to image. I have number of images in db...so when I using for loop it throws error Parameter is not valid...without for loop it works fine.

//get image in system.byte[] format...so convert here in img format...

         public System.Drawing.Image ByteArrayToImage(byte[] data)
          {
              MemoryStream bipimag = new MemoryStream(data);
              System.Drawing.Image  imag = new Bitmap(bipimag);
               return imag;
          }

On button submit -

                            System.Drawing.Image img2 = null;
                            System.Drawing.Image img3 = null;

                             for (int i = 0; i <= dt4.Rows.Count - 1; i++)
                                {
                                img2 = ByteArrayToImage((byte[])dt4.Rows[i][5]);         //Parameter is not valid
                                img3 = ByteArrayToImage((byte[])dt4.Rows[i][6]);
                                }