在WPF MVVM中,我是否有必要将所有要绑定的属性作为依赖项属性包装？

Question

我正在编写一个带有大规模数据模型的应用程序 - 作为其中的一部分,我第一次使用MVVM模式.有很多用于管理各种实体的屏幕,因此有很多视图模型.我发现每个视图模型都将我正在使用的POCO实体的每个属性包装在依赖项属性中,这样我就可以将它绑定到编辑器字段,然后在用户提交更改时将其写回实体.这对我来说感觉就像是一大堆额外的腿部工作,我不禁想知道我是否错过了这一点,或者是否有更简单的方法来实现我的目标.举个例子,我有一个地址视图模型:

public class AddressViewModel : EntityViewModel<Address>
{
    #region Properties

    public string AddressLine1
    {
        get { return (string) GetValue(AddressLine1Property); }
        set { SetValue(AddressLine1Property, value); }
    }

    // Using a DependencyProperty as the backing store for AddressLine1.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty AddressLine1Property =
        DependencyProperty.Register("AddressLine1", typeof (string), typeof (AddressViewModel), new PropertyMetadata(string.Empty, HandleAddressChange));

    private static void HandleAddressChange(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var vm = d as AddressViewModel;
        if (vm != null)
        {
            vm.OnPropertyChanged(AddressAsSingleLineStringPropertyName);
        }
    }

    public string AddressLine2
    {
        get { return (string) GetValue(AddressLine2Property); }
        set { SetValue(AddressLine2Property, value); }
    }

    // Using a DependencyProperty as the backing store for AddressLine2.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty AddressLine2Property =
        DependencyProperty.Register("AddressLine2", typeof (string), typeof (AddressViewModel), new PropertyMetadata(string.Empty));

    public string AddressLine3
    {
        get { return (string) GetValue(AddressLine3Property); }
        set { SetValue(AddressLine3Property, value); }
    }

    // Using a DependencyProperty as the backing store for AddressLine2.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty AddressLine3Property =
        DependencyProperty.Register("AddressLine3", typeof (string), typeof (AddressViewModel), new PropertyMetadata(string.Empty));

    public string AddressLine4
    {
        get { return (string) GetValue(AddressLine4Property); }
        set { SetValue(AddressLine4Property, value); }
    }

    // Using a DependencyProperty as the backing store for AddressLine2.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty AddressLine4Property =
        DependencyProperty.Register("AddressLine4", typeof (string), typeof (AddressViewModel), new PropertyMetadata(string.Empty));

    public string AddressLine5
    {
        get { return (string) GetValue(AddressLine5Property); }
        set { SetValue(AddressLine5Property, value); }
    }

    // Using a DependencyProperty as the backing store for AddressLine2.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty AddressLine5Property =
        DependencyProperty.Register("AddressLine5", typeof (string), typeof (AddressViewModel), new PropertyMetadata(string.Empty));

    public string PostCode
    {
        get { return (string) GetValue(PostCodeProperty); }
        set { SetValue(PostCodeProperty, value); }
    }

    // Using a DependencyProperty as the backing store for PostCode.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty PostCodeProperty =
        DependencyProperty.Register("PostCode", typeof (string), typeof (AddressViewModel), new PropertyMetadata(string.Empty, HandleAddressChange));

    /// <summary>
    ///   Gets a value indicating whether this instance is valid for save.
    /// </summary>
    /// <value> <c>true</c> if this instance is valid for save; otherwise, <c>false</c> . </value>
    /// <exception cref="System.NotImplementedException"></exception>
    public override bool IsValidForSave
    {
        get { return !string.IsNullOrWhiteSpace(AddressLine1); }
    }


    /// <summary>
    ///   Gets a value indicating whether this instance is valid for edit.
    /// </summary>
    /// <value> <c>true</c> if this instance is valid for edit; otherwise, <c>false</c> . </value>
    public override bool IsValidForEdit
    {
        get { return true; }
    }



    #endregion

    #region Constructor

    /// <summary>
    /// Initializes a new instance of the <see cref="AddressViewModel" /> class.
    /// </summary>
    public AddressViewModel(Address address) : base(address)
    {
    }

    #endregion

    #region Private Methods

    /// <summary>
    ///   Sets the properties from entity.
    /// </summary>
    public override void SetPropertiesFromEntity()
    {
        AddressLine1 = Entity.AddressLine1;
        AddressLine2 = Entity.AddressLine2;
        AddressLine3 = Entity.AddressLine3;
        AddressLine4 = Entity.AddressLine4;
        AddressLine5 = Entity.AddressLine5;
        PostCode = Entity.PostCode;
    }

    /// <summary>
    ///   Sets the entity from properties.
    /// </summary>
    public override void SetEntityFromProperties()
    {
        Entity.AddressLine1 = AddressLine1;
        Entity.AddressLine2 = AddressLine2;
        Entity.AddressLine3 = AddressLine3;
        Entity.AddressLine4 = AddressLine4;
        Entity.AddressLine5 = AddressLine5;
        Entity.PostCode = PostCode;
    }
}

这是一个简单的五个属性实体的包装.

将此与MVC Web应用程序的腿部工作相比较,我只是为该模型生成一个编辑器,并且我们在开销方面存在相当严重的差异,因此我可以双向绑定一堆文本框.我更愿意有人告诉我,我已经错过了这一点,并且我完全错误地做了这一点,但据我所知,我的实体是我的模型,viewmodel包装它,视图绑定到viewmodel.我查看了MVVM框架,但它们似乎更倾向于帮助控制程序流并管理视图集和视图模型,而不是减少创建视图模型的工作量.

Answer 1

您根本不需要这些DependencyProperties.我建议你将它们作为标准属性实现.

如果您的viewmodel可能在显示UI时发生更改,并且您希望该更改反映在UI中,则需要实现该INotifyPropertyChanged界面.您可以使用Fody PropertyChanged库(可通过Nuget获得)轻松完成此操作,如果您只是为类添加属性,它将为您完成所有的工作.

您真正需要依赖项属性的唯一情况是,是否在Xaml中设置了该属性的值,并且您希望使用a MarkupExtension(例如,使用Binding或x:Static)设置该值.在你的情况下,你将绑定应用于控件上的属性(我猜Textbox.Text),所以它TextBox.Text就是一个DependencyProperty.

Answer 2

虽然我并不完全清楚你的代码究竟想要实现什么,但我相信在这种情况下你不需要依赖属性,而只需要普通属性(可能还有INotifyPropertyChanged接口).在创建控件时,将使用依赖项属性,其中该控件的属性将绑定到视图模型中的属性.如果您只是尝试将视图模型绑定到现有控件,那么只需要简单的属性.