title: load a datatable to an existing table in dataset
body: <p>how can in load a <code>DataTable</code> to an existing table in my <code>DataSet</code>. something like this:</p>
  
  <pre><code>DataTable my_table = new DataTable("sale_info");
  **add some row to my_table **
  myDataSet.Tables.Add(my_table);
  </code></pre>
  
  <p>i have a table named <code>sale_info</code> in myDataset too and <code>myDataSet.Tables.Add(my_table);</code> is trying to add new one. actually i want update my table with new data from another table.</p>