private void Check_Passowrd() { String UsernameStr = UsernameTextBox.Text.ToString(); String PasswordStr = Password_Box.Password.ToString(); db = new ERP_DBEntities(); var LoginQuery = from d in db.user where d.Username == UsernameStr select d.Password; //Find password in db Boolean IsLoginSuccess = false; foreach (String StrInQuery in LoginQuery.ToList()) { if (StrInQuery == PasswordStr) { IsLoginSuccess = true; break; } } if (IsLoginSuccess) { ChoseFuncWindow choseFuncWindow = new ChoseFuncWindow(); choseFuncWindow.Show(); } else { MessageBox.Show("用户名和密码错误,请检查。", "登录失败!"); } }