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WPF MVVM中的两个“自更新”属性

mvvm architecture wpf

Tom Deleu · 技术社区 · 16 年前

考虑到您有一个类似WPF的MVVM体系结构 Josh Smith's examples

如何实现两个相互更新的“同步”属性?我的模型中有Price属性和PriceVatienclusive属性。

-当价格变化时,我想看到增值税包含价格自动为“价格*1.21”。

-反之亦然,当pricevaticlusive发生变化时,我希望价格为“pricevaticlusive/1.21”

有什么想法吗?

如果您的模型是实体框架实体呢?你不能用上面的方法…不?你应该把计算代码放在视图模型中还是…?

2 回复 | 直到 12 年前

Szymon Rozga 16 年前

一种方式:

    public class Sample : INotifyPropertyChanged
    {
        private const double Multiplier = 1.21;
        #region Fields
        private double price;
        private double vat;
        #endregion

        #region Properties
        public double Price
        {
            get { return price; }
            set
            {
                if (price == value) return;
                price = value;
                OnPropertyChanged(new PropertyChangedEventArgs("Price"));
                Vat = Price * Multiplier;
            }
        }

        public double Vat
        {
            get { return vat; }
            set
            {
                if (vat == value) return;
                vat = value;
                OnPropertyChanged(new PropertyChangedEventArgs("Vat"));
                Price = Vat / Multiplier;
            }
        }
        #endregion

        #region INotifyPropertyChanged Members
        protected void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            PropertyChangedEventHandler ev = PropertyChanged;
            if (ev != null)
            {
                ev(this, e);
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;

        #endregion
    }

如果可以从DependencyObject派生,则可以使用依赖属性。

public class Sample : DependencyObject
{
    private const double Multiplier = 1.21;

    public static readonly DependencyProperty VatProperty =
        DependencyProperty.Register("Vat", typeof(double), typeof(Sample), 
        new PropertyMetadata(VatPropertyChanged));

    public static readonly DependencyProperty PriceProperty =
        DependencyProperty.Register("Price", typeof(double), typeof(Sample), 
        new PropertyMetadata(PricePropertyChanged));

    private static void VatPropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        Sample sample = obj as Sample;
        sample.Price = sample.Vat / Multiplier;
    }

    private static void PricePropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        Sample sample = obj as Sample;
        sample.Vat = sample.Price * Multiplier;
    }

    #region Properties
    public double Price
    {
        get { return (double)GetValue(PriceProperty); }
        set { SetValue(PriceProperty, value); }
    }

    public double Vat
    {
        get { return (double)GetValue(VatProperty); }
        set { SetValue(VatProperty, value); }
    }
    #endregion
}

Arnaud 12 年前

看一看 Polymod.NET . 如果域对象上有“price”属性,则可以为该域类创建模型,定义公式“pricevat”=price*0.1。模型将知道价格变化时pricevat会发生变化,并将其告知用户界面。

你的域名类甚至不需要是无效的!