title: Set autonumber for DataTable after it already has data
body: <p>I have the following code to add an autonumber column to a <code>DataTable</code>:</p>
  
  <pre><code>public void AddAutoIncrementColumn(DataTable dt)
  {
     DataColumn column = new DataColumn();
     column.DataType = System.Type.GetType("System.Int32");
     column.AutoIncrement = true;
     column.AutoIncrementSeed = 0;
     column.AutoIncrementStep = 1;
     dt.Columns.Add(column);
  }
  </code></pre>
  
  <p>However, this value will be blank for all rows that are already in the table; it seems that the AutoIncrement is only triggered for new rows that are added after this column has been added.  Is there a way to set autonumber values for the rows that already exist?</p>