public bool CheckLogin(string username, string password, int mode)
        {
            DataSet ds = new DataSet();
            if (username == "" || password == "")
            {
                fault = new InfoFault();
                fault.Type = "ArgumentException";
                fault.Message = "Username and Password is not null";
                throw new FaultException<InfoFault>(fault);
            }
            else
            {
                switch (mode)
                {
                    case 0:
                        {
                            string query = "Select * From tbl_SinhVien Where MSSV = '" + username + "' And MatKhau = '" + password + "'";
                            try
                            {
                                connect.Open_Connect();
                                SqlDataAdapter adap = new SqlDataAdapter(query, connect.con);
                                adap.Fill(ds);
                                connect.Close_Connect();
                                if (ds.Tables[0].Rows.Count != 0)
                                {
                                    return true;
                                }
                                else
                                    return false;
                            }
                            catch (Exception)
                            {

                                return false;
                            }
                        }
                    case 1:
                        {
                            string query = "Select * From tbl_SinhVien Where MSSV = '" + username + "' And MatKhauGD = '" + password + "'";
                            try
                            {
                                connect.Open_Connect();
                                SqlDataAdapter adap = new SqlDataAdapter(query, connect.con);
                                adap.Fill(ds);
                                connect.Close_Connect();
                                if (ds.Tables[0].Rows.Count != 0)
                                {
                                    return true;
                                }
                                else
                                    return false;
                            }
                            catch (Exception)
                            {

                                return false;
                            }

                        }
                    case 2:
                        {
                            string query = "Select * From tbl_GiangVien Where MSGV = '" + username + "' And MatKhau = '" + password + "'";
                            try
                            {
                                connect.Open_Connect();
                                SqlDataAdapter adap = new SqlDataAdapter(query, connect.con);
                                adap.Fill(ds);
                                connect.Close_Connect();
                                if (ds.Tables[0].Rows.Count != 0)
                                {
                                    return true;
                                }
                                else
                                    return false;
                            }
                            catch (Exception)
                            {

                                return false;
                            }

                        }
                    default: { return false; }
                }
            }
        }
 public bool Update_Info_Stu(Student Stu)
 {
     lstFault = new List<InfoFault>();
     if (Stu.Diachi == "" || Stu.Dantoc == "" || Stu.Quoctich == "" || Stu.Tongiao == "")
     {
         fault = new InfoFault();
         fault.Type = "Required Info";
         fault.Message = "Yêu cầu nhập đầy đủ các thông bắt buộc (*): Địa chỉ, Quốc tịch, Dân tộc, Tôn giáo";
         lstFault.Add(fault);
     }
     if (Stu.Dienthoai != "")
     {
         if (IsNumber(Stu.Dienthoai) == false)
         {
             fault = new InfoFault();
             fault.Type = "Correctness";
             fault.Message = "Số điện thoại phải là số";
             lstFault.Add(fault);
         }
         else if (Stu.Dienthoai.Length < 8 || Stu.Dienthoai.Length > 12)
         {
             fault = new InfoFault();
             fault.Type = "Correctness";
             fault.Message = "Số điện thoại ít nhất 8 số, nhiều nhất 12 số";
             lstFault.Add(fault);
         }
     }
     if (Stu.Email != "")
     {
         if (IsValidEmail(Stu.Email) == false)
         {
             fault = new InfoFault();
             fault.Type = "Correctness";
             fault.Message = "Email không đúng dạng";
             lstFault.Add(fault);
         }
     }
     if (lstFault.Count != 0)
         throw new FaultException<InfoFault[]>(lstFault.ToArray());
     else
     {
         connect.Open_Connect();
         string query = "Update tbl_SinhVien" +
             " Set DiaChi = N'" + Stu.Diachi + "', DienThoai = '" + Stu.Dienthoai + "', Email = '" + Stu.Email + "', QuocTich = N'" + Stu.Quoctich +
             "', TonGiao = N'" + Stu.Tongiao + "', DanToc = N'" + Stu.Dantoc + "',HoTenCha = N'" + Stu.Hotencha + "', NgheNghiepCha = N'" + Stu.Nghenghiepcha + "', HoTenMe = N'" + Stu.Hotenme + "', NghenghiepMe = N'" + Stu.Nghenghiepme + "'" +
                        " Where MSSV = '" + Stu.Mssv + "'";
         SqlCommand cmd = new SqlCommand(query, connect.con);
         int roweff = cmd.ExecuteNonQuery();
         connect.Close_Connect();
         if (roweff != 0)
         {
             return true;
         }
         else
             return false;
     }
 }