public void FormUserManager_Load(object sender, EventArgs e)
 {
     mySource.DataSource             = db.GetUser();
     this.staffName.DataSource       = db.GetAllStaff();
     this.staffName.DisplayMember    = "staff_name";
     this.staffName.ValueMember      = "staff_id";
     this.staffName.DataPropertyName = "staff_name";
 }