SqlCommand cmd = new SqlCommand("update Users set Username=@Username,Password=@Password,Name=@Name,Address=@Address,Phone=@Phone,@Email=Email,@RoleId=RoleId", conn);
            cmd.Parameters.AddWithValue("@Username", username.Text);
            cmd.Parameters.AddWithValue("@Password", password.Text);
            cmd.Parameters.AddWithValue("@Name", name.Text);
            cmd.Parameters.AddWithValue("@Address", address.Text);
            cmd.Parameters.AddWithValue("@Phone", phone.Text);
            cmd.Parameters.AddWithValue("@Email", email.Text);
            cmd.Parameters.AddWithValue("@RoleId", DropDownList4.SelectedItem);
            conn.Open();
            cmd.ExecuteNonQuery();
            conn.Close();