在WPF中登录验证后导航到UserControl？

Question

我有一个登录用户控件和一个ModuleHomeScreen用户控件。

我的登录UserControl有一个用户名和密码文本框以及一个LoginButton。 当用户单击LoginButton时，将从数据库验证其凭据； 然后必须将他导航到ModuleHomeScreen UserControl。

UserCredentials验证工作正常。 MainWindow有一个NavigationFrame，我可以在其中切换UserControl。

现在我的问题是：在不填写用户凭据的情况下，当用户单击登录按钮时，他仍会导航到仪表板UserControl。 导航代码甚至还有问题！

如何首先验证登录凭据，如果成功，则导航到其他UserControl？

这是我的代码附件：

Login.xaml

    public void loginButton_Click(object sender, EventArgs e)
    {
        if (LoginUserName.Text != "" && LoginPassword.Password != "")
        {
            NpgsqlConnection con = new NpgsqlConnection("Server=localhost;Port=1234;UserID=postgres;Password=root;Database=postgres");
            con.Open();
            String username = LoginUserName.Text.Trim();
            String encPassword = TripleDESCrypto.Encrypt(LoginPassword.Password.Trim(),true);
            String query = "SELECT * FROM login where username= '" + username + "' and password = '" + encPassword + "';";
            NpgsqlCommand cmd = new NpgsqlCommand(query, con);
            NpgsqlDataReader dr = cmd.ExecuteReader();
            if (dr.Read())
            {
               // ServiceContainer.GetService<INavigationService>().Navigate("ModuleHomeScreen", null, this);
                LoginErrorMessage.Text = "Login Successfull";
                MainWindow appWindow = new MainWindow();
                ModuleHomeScreen appScreen = new ModuleHomeScreen();
                appWindow.MainWindowNavigationFrame.Navigate(appScreen,null);
            }
            else
            {
                LoginErrorMessage.Text = "Invalid Login Credentials.";
            }
        }
        else
        {
            LoginErrorMessage.Text = "Please enter all fields !";
        }
    }

Answer 1

尝试这个 ：

    public void loginButton_Click(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(LoginUserName.Text))
        {
            ////Password could be empty for some user's
            if (LoginPassword.Password == null)
                LoginPassword.Password = string.Empty;

            NpgsqlConnection con = new NpgsqlConnection("Server=localhost;Port=1234;UserID=postgres;Password=root;Database=postgres");
            con.Open();
            String username = LoginUserName.Text.Trim();
            String encPassword = TripleDESCrypto.Encrypt(LoginPassword.Password.Trim(), true);
            String query = "SELECT count(*) FROM login where username= '" + username + "' and password = '" + encPassword + "';";
            NpgsqlCommand cmd = new NpgsqlCommand(query, con);
            int? dr = cmd.ExecuteScalar() as int?;
            if (dr.HasValue && dr.Value > 0)
            {
                // ServiceContainer.GetService<INavigationService>().Navigate("ModuleHomeScreen", null, this);
                LoginErrorMessage.Text = "Login Successfull";
                MainWindow appWindow = new MainWindow();
                ModuleHomeScreen appScreen = new ModuleHomeScreen();
                appWindow.MainWindowNavigationFrame.Navigate(appScreen, null);
            }
            else
            {
                LoginErrorMessage.Text = "Invalid Login Credentials.";
            }
        }
        else
        {
            LoginErrorMessage.Text = "Please enter user name !";
        }
    }