title: Multipart Identifier "arafa.almahmud08@gmail.com" couldnot be bound
body: <p>I have built a custom validator,</p>
  
  <p>I have a sql query like this:</p>
  
  <pre><code>protected void custom_serverValidate(object sender, ServerValidateEventArgs e)
      {
          connect();
          string strSQL = "select EmailAddress from Accounts_Users where EmailAddress=" + REmailTextBox.Text;
          SqlCommand cmd = new SqlCommand(strSQL, objConnection);
          if (e.Value.ToString() == cmd.ExecuteScalar().ToString())
          {
              e.IsValid = false;
          }
          else
              e.IsValid = true;
          disConnect();
      }
  </code></pre>
  
  <p>when I execute my code in the browser and an email address and submit it , I get the error mentioned in the title. how to fix it ?</p>