c# - WPF MVVM 登录凭据

Question

我是 WPF 和 MVVM 的新手，但我在理解方面取得了进展。有一个问题让我有点困惑。我有一个带有关联 ViewModel 的登录页面，用于登录应用程序。但是，每次我使用我知道正确的凭据时，它都会返回“用户名不正确”消息框。它应该打开到 WindowMain 窗口。也许是文本框绑定(bind)的问题？任何帮助将不胜感激。谢谢!

可观察对象

public abstract class ObservableObject : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propName)
    {
        Debug.Assert(GetType().GetProperty(propName) != null);

        var pc = PropertyChanged;
        if (pc != null)
        {
            pc(this, new PropertyChangedEventArgs(propName));
        }
    }

    protected bool SetProperty<T>(ref T field, T value, string propName)
    {
        if (!EqualityComparer<T>.Default.Equals(field, value))
        {
            field = value;
            OnPropertyChanged(propName);
            return true;
        }

        return false;
    }

    protected bool SetProperty<T>(ref T field, T value, Expression<Func<T>> expr)
    {
        if (!EqualityComparer<T>.Default.Equals(field, value))
        {
            field = value;
            var lambda = (LambdaExpression)expr;
            MemberExpression memberExpr;

            if (lambda.Body is UnaryExpression)
            {
                var unaryExpr = (UnaryExpression)lambda.Body;
                memberExpr = (MemberExpression)unaryExpr.Operand;
            }
            else
            {
                memberExpr = (MemberExpression)lambda.Body;
            }

            OnPropertyChanged(memberExpr.Member.Name);
            return true;
        }

        return false;
    }
}

登录中继命令

public class LoginRelayCommand : ICommand
{
    private Action<object> execute;
    private Func<object, bool> canExecute;

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    public LoginRelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
    {
        this.execute = execute;
        this.canExecute = canExecute;
    }

    public bool CanExecute(object parameter)
    {
        return this.canExecute == null || this.canExecute(parameter);
    }

    public void Execute(object parameter)
    {
        this.execute(parameter);
    }
}

View 模型

public class LoginWindowVM : ObservableObject
{
    private ICommand _submitLoginButton;

    private Textbox1 _textbox1Input;
    private Textbox2 _textbox2Input;

    public ICommand SubmitLoginButton
    {
        get
        {
            if(_submitLoginButton == null)
            {
                _submitLoginButton = new LoginRelayCommand(param => this.SubmitButton(), null);
            }

            return _submitLoginButton;
        }
    }

    public Textbox1 Textbox1Input
    {
        get { return _textbox1Input; }
        set { SetProperty(ref _textbox1Input, value, () => Textbox1Input); }
    }

    public Textbox2 Textbox2Input
    {
        get { return _textbox2Input; }
        set { SetProperty(ref _textbox2Input, value, () => Textbox2Input); }
    }

    public LoginWindowVM() : base()
    {
        _textbox1Input = new Textbox1();
        _textbox2Input = new Textbox2();
    }

    private void SubmitButton()
    {
        MySqlConnection dbConnectionString = new MySqlConnection(@"datasource=localhost;port=3306;Initial Catalog='optest1a1';username=root;password=");
        try
        {
            if (dbConnectionString.State == System.Data.ConnectionState.Closed)
                dbConnectionString.Open();
            String query = "SELECT COUNT(1) FROM users_sw WHERE Username=@Username AND Password=@Password";
            MySqlCommand cmd = new MySqlCommand(query, dbConnectionString);
            cmd.CommandType = System.Data.CommandType.Text;
            cmd.Parameters.AddWithValue("@Username", Textbox1Input);
            cmd.Parameters.AddWithValue("@Password", Textbox2Input);
            int count = Convert.ToInt32(cmd.ExecuteScalar());
            if (count == 1)
            {
                WindowMain dashboard = new WindowMain();
                dashboard.Show();
                dbConnectionString.Close();
            }
            else
            {
                MessageBox.Show("Username or Password Is Incorrect");
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
        finally
        {
            dbConnectionString.Close();
        }
    }
}

查看

    <Grid>
    <Label x:Name="lblUsername" Content="Username" HorizontalAlignment="Left" Margin="45,57,0,0" VerticalAlignment="Top"/>
    <Label x:Name="lblPassword" Content="Password" HorizontalAlignment="Left" Margin="48,104,0,0" VerticalAlignment="Top"/>
    <TextBox x:Name="txtUsername" Text="{Binding Textbox1Input, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" 
             HorizontalAlignment="Left" Height="23" Margin="128,60,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
    <TextBox x:Name="txtPassword" Text="{Binding Textbox2Input, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" 
             HorizontalAlignment="Left" Height="23" Margin="128,108,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
    <Button x:Name="btnSubmit" Content="Submit" HorizontalAlignment="Left" Margin="118,175,0,0" VerticalAlignment="Top" Width="75"
            Command="{Binding SubmitLoginButton}"
            />
</Grid>

View.cs

    public partial class LoginWindow : Window
{
    private LoginWindowVM _viewModel;

    public LoginWindow()
    {
        InitializeComponent();

        _viewModel = new LoginWindowVM();
        this.DataContext = _viewModel;
    }
}

Answer 1

您正在绑定(bind)到 TextBox Text 属性，该属性期望 string 作为源并且您正在绑定(bind)到 Textbox 本身。只需将其更改为 String 属性:

private String_textbox1Input;

public String Textbox1Input
{
    get { return _textbox1Input; }
    set { SetProperty(ref _textbox1Input, value, () => Textbox1Input); }
}

注意:文本框默认绑定(bind)模式是TwoWay，显式设置它是没有用的