title: Table doesn't have primary key c#
body: <p>Im trying to delete rows from <code>DataTable AllItems</code> with rows from <code>DataTables Items</code>; The purpose of this to get items from <code>DataTable AllItems</code> which are not inside <code>DataTable Items</code></p>
  
  <p><strong>All these rows Fiiled from same Excel file which contains several columns and are equal.</strong></p>
  
  <p>I have tried using foreach loop:</p>
  
  <pre><code>foreach(DataRow dr in AllItems.Rows)
  {
  if (Items.Contains(dr))
  {
  AllItems.Rows.Remove(dr);
  }
  </code></pre>
  
  <p>But I get following error: Table doesn't have primary key. </p>
  
  <p>Does anyone knows how i can delete these rows? </p>