title: [InvalidCastException: Unable to cast object of type 'System.DBNull' to type 'System.String'.]
body: <p>The error line:</p>
  
  <p>Source Error: </p>
  
  <pre><code>Line 37:         while (rdr.Read()==true)
  Line 38:         {
  Line 39:             if (TextBoxUserName.Text == (string)rdr["CUserName"]) 
  Line 40:             {
  Line 41:                 ClientScript.RegisterStartupScript(csType,"Error",scriptErrorUserId);
  </code></pre>
  
  <p>It pops up when I tried to register an account.</p>
  
  <p>I use microsoft access as database. </p>
  
  <p>Database - CUserName
  Session - sUserName
  and there's @eUserName</p>
  
  <p>any idea guys?</p>