title: Add value (Row) if not exists already in the gridview
body: <p>I want to add some rows in datagridview (without binding) from a combobox text property.
  but I need first to check if it is already added, it yes then show a message, if not already added, then add the text value of the combo in the gridview.
  I am using VS 2010 with C#
  I search a lot of all available solutions but not working with me.</p>
  
  <p>I tried to loop on the rows but I couldn't do it,, please help!!</p>
  
  <p>this is my code to add the value but how to check?</p>
  
  <pre><code>dgv_standards.Rows.Add(cbo_standard.SelectedValue.ToString(), cbo_standard.Text);
  </code></pre>