title: Datagridview column SUM to textbox & update textbox with each adding row
body: <p>I'm new to C# &amp; i need your help with my below problem.
  I've DGV &amp; its not bound to any data source. I have few textboxes &amp; datetimepicker to add data to DGV. Once the user press the "ADD" button in my form it will add new row to the DGV. My problem is i need to get the SUM of column 4th in my DGV in to a textbox in my form which is the total bill value. And it should be updated with each adding rows column 5th values</p>
  
  <p>Hope you guys understood my problem. Sorry for my bad English. any codes are welcome.</p>
  
  <pre><code>textBox10.Text = "0";
             foreach (DataGridViewRow row in dgvFE.Rows)
             {
                int n1 = row.Index;
                textBox10.Text = (Double.Parse(textBox10.Text.ToString()) + Double.Parse(dgvFE.Rows[n].Cells[4].Value.ToString())).ToString();
  
  
             }
  </code></pre>
  
  <p>I have entered above code under "ADD" button click event. But my textbox10 is showing only first line of bill value. not the SUM of all rows in column 5th. (User can add more columns as i mentioned earlier.)</p>
  
  <p>I have try below code under the same button click event but the result in textbox10 is same like above code.</p>
  
  <pre><code>int sum = 0;
  for (int x = 0; x &lt; dgvFE.Rows.Count; x++ )
  {
    sum += Convert.ToInt32(dgvFE.Rows[x].Cells[4].Value);
  }
  </code></pre>
  
  <p>Please help.</p>