title: Sum datagridview cells with comma generates a format exception
body: <p>I'm using this code for sum datagridview's cells.</p>
  
  <pre><code>int sum = 0;
  for (int i = 0; i &lt; dataGridView1.Rows.Count; ++i)
  {
  sum += Convert.ToInt32 (dataGridView1.Rows[i].Cells[1].Value);
  }
  int count_row = dataGridView1.Rows.Count;
  
  label1.Text = (sum.ToString());
  </code></pre>
  
  <p>The code works well if I just use numbers. However, when I use commas, e.g., 1,34 and 2,20, it says that format exception was unhandled.</p>