title: Items collection cannot be modified when the DataSource property is set. c#
body: <p>I am getting the error while I am trying to <strong>insert a new item</strong> into combo box</p>
  
  <p><strong>Error: Items collection cannot be modified when the DataSource property is set.</strong></p>
  
  <pre><code>string connectionstring = "MultipleActiveResultSets=True;Data Source=ECSTSRD;Initial Catalog=PMIDB;User ID=pnpuser;Password=pnpuser123";
  sqlConnection myconnection = new SqlConnection(connectionstring);
  
  myconnection.Open();
  string custPOsql = "INSERT INTO cust_po (cust_code, po_no) VALUES (@cust_code, @po_no)";
         SqlCommand custPOcom = new SqlCommand(custPOsql, myconnection);
         custPOcom.Parameters.AddWithValue("@cust_code", cboCustCode.Text);
         custPOcom.Parameters.AddWithValue("@po_no", cboPO.Text);
         custPOcom.ExecuteNonQuery();
         MessageBox.Show("Insert Successfully", "Insert");
         cboPO.Items.Add(cboPO.Text);
  </code></pre>
  
  <p>FYI, I bind the data source of PO combobox in form load.</p>
  
  <p>I have found few similar question in stackoverflow as well as others forums, the way they mention is using <code>cboPO.Items.Add(cboPO.Text)</code> to add new item into combo box, but I could not use it as error shown.</p>
  
  <p>Do anyone know what is the problem, please help.</p>
  
  <p>Thanks in advance.</p>