title: Required field validation on textbox
body: <pre><code>          try
          {
              Connections.con.Open();
              string str = "INSERT INTO `Employee` (`FirstName`, `LastName`, `DOB`, `ContactNumber`, `Username`, `Password`) VALUES (?, ?, ?, ?, ?, ?)";
              OleDbCommand cmd = new OleDbCommand(str, Connections.con);
              cmd.Parameters.AddWithValue("@?", txtFirst.Text.ToString());
              cmd.Parameters.AddWithValue("@?", txtLast.Text.ToString());
              cmd.Parameters.AddWithValue("@?", txtDOB.Text.ToString());
              cmd.Parameters.AddWithValue("@?", txtCon.Text.ToString());
              cmd.Parameters.AddWithValue("@?", txtUser.Text.ToString());
              cmd.Parameters.AddWithValue("@?", txtPass.Text.ToString());
  
  
              cmd.ExecuteNonQuery();
  
              MessageBox.Show("Registration Successful");
          }
          catch (Exception ex)
          {
              MessageBox.Show("Username Exists.");
          }
          finally
          {
  
              Connections.con.Close();
              this.Dispose();
              this.Close();
              f1.Show();
          }
  </code></pre>
  
  <p>I can't find a way that the form will prompt a message that says Please fill up the empty field..
  whenever the user forgot to fill the text box </p>