public void XoaNhanVien(string ma)
        {
            NHAN_VIEN nv = data.NHAN_VIENs.Where(t => t.MaNV == ma).FirstOrDefault();

            data.NHAN_VIENs.DeleteOnSubmit(nv);
            data.SubmitChanges();
        }
        public NHAN_VIEN TimTaiKhoanNhanVien(string taiKhoan)
        {
            DANG_NHAP dn = data.DANG_NHAPs.Where(t => t.TaiKhoan == taiKhoan).FirstOrDefault();
            NHAN_VIEN nv = data.NHAN_VIENs.Where(t => t.MaNV == dn.MaNV).FirstOrDefault();

            return(nv);
        }
        public void SuaNhanVien(string ma, string ten, string email, string cmnd, string dt, DateTime ngay, string chucVu)
        {
            NHAN_VIEN nv = data.NHAN_VIENs.Where(t => t.MaNV == ma).FirstOrDefault();

            nv.TenNV    = ten;
            nv.Email    = email;
            nv.CMND     = cmnd;
            nv.SDT      = dt;
            nv.NgaySinh = ngay;
            nv.MaCV     = chucVu;
            data.SubmitChanges();
        }
        public void ThemNhanVien(string ma, string ten, string email, string cmnd, string dt, DateTime ngay, string chucVu)
        {
            NHAN_VIEN nv = new NHAN_VIEN();

            nv.MaNV     = ma;
            nv.TenNV    = ten;
            nv.Email    = email;
            nv.CMND     = cmnd;
            nv.SDT      = dt;
            nv.NgaySinh = ngay;
            nv.MaCV     = chucVu;
            data.NHAN_VIENs.InsertOnSubmit(nv);
            data.SubmitChanges();
        }
        public NHAN_VIEN TimNhanVien(string ma)
        {
            NHAN_VIEN nv = data.NHAN_VIENs.Where(t => t.MaNV == ma).FirstOrDefault();

            return(nv);
        }
        public bool KiemTraKhoaChinh(string ma)
        {
            NHAN_VIEN nv = data.NHAN_VIENs.Where(t => t.MaNV == ma).FirstOrDefault();

            return(nv != null);
        }