copy DataRow from one DataTable to another?

I have a very 开发者_运维技巧specific requirement. I've two datatables (both of same schema) one table(aqTable) with 2 rows and another (rapidsTable) with 5 rows. I need to check if those 2 rows in aqTable are present in those 5 rows of rapidsTable or not, if those two rows are present in rapidsTable then copy remaining (difference) 3 rows to aqTable.

I tried it in this way, but when it loops over for 3rd row throws an exception "There is no row a position2" because there are no more than 2 rows in one of the table.

if (rapidsTable.Rows.Count > aqTable.Rows.Count)
{
try
  {
    int aqRow = 0; rows = 0;
    int rCount = rapidsTable.Rows.Count;
    for (int rRow = 0; rRow < rCount; rRow++)
    {
      if (aqTable.Rows.Count == 0)
      {
         DataRow row = aqTable.NewRow();
         row.ItemArray = rapidsTable.Rows[aqRow].ItemArray;
         rowStr += rapidsTable.Rows[rRow][0].ToString() + ",";
         aqTable.Rows.Add(row); rows++;
      }
      else
      {
         string str = aqTable.Rows[aqRow].ToString();
         if (aqTable.Rows.ToString() == null || aqTable.Rows.ToString() == "") 
         { }
         if ((aqTable.Rows[aqRow][1].ToString() == rapidsTable.Rows[rRow][1].ToString()) &&
             (aqTable.Rows[aqRow][2].ToString() == rapidsTable.Rows[rRow][2].ToString()) &&
             (aqTable.Rows[aqRow][3].ToString() == rapidsTable.Rows[rRow][3].ToString()))
         { }
         else
         {
             DataRow row = aqTable.NewRow();
             row.ItemArray = rapidsTable.Rows[aqRow].ItemArray;
             rowStr += rapidsTable.Rows[rRow][0].ToString() + ",";
             aqTable.Rows.Add(row); rRow = rRow - 1; rows++;
          }
      }
     aqRow++;
    }  
catch (Exception ex)
{ throw new Exception("R>AQ Copy: " + ex.Message); }

Is there a way to solve this for that exception. I tried many different ways from many different blogs. Found this blog has some best examples, thought to share my problem.

I think this is what you are looking for

http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q308909