WPF MVVM - 如何调用外部服务 (WCF) 来更新模型 OnPropertyChanged？

Question

我的 WPF 应用程序中有模型和视图模型，如下所示。

我的目的是在 GivenPrice 更改时用 WCF 中的一些字符串更新 HumanizedPrice 属性。 HumanizedPrice基于GivenPrice，需要WCF才能获取。为此，最好的 MVVM 兼容方法是什么？

型号：

class Price : INotifyPropertyChanged
{
    public string GivenPrice
    {
        get
        {
            return _givenPrice;
        }

        set
        {
            if (_givenPrice != value)
            {
                _givenPrice = value;
                RaisePropertyChanged("GivenPrice");
                RaisePropertyChanged("HumanizedPrice");
            }
        }
    }

    public string HumanizedPrice
    {
        get
        {
            return _humanizedPrice;
        }

        set
        {
            if (_humanizedPrice != value)
            {
                _humanizedPrice = value;
                RaisePropertyChanged("HumanizedPrice");
            }
        }
    }

    private string _givenPrice;
    private string _humanizedPrice;

    public event PropertyChangedEventHandler PropertyChanged;

    private void RaisePropertyChanged(string property)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));            
    }
}

视图模型：

class PriceViewModel
{

    public PriceViewModel()
    {
        LoadPrices();
    }

    public ObservableCollection<Price> Prices
    {
        get;
        set;
    }

    public void LoadPrices()
    {
        ObservableCollection<Price> prices = new ObservableCollection<Price>();

        prices.Add(new Price { GivenPrice = "221 331,44" });
        prices.Add(new Price { GivenPrice = "2 331,44" });
        prices.Add(new Price { GivenPrice = "331,44" });
        prices.Add(new Price { GivenPrice = "0,44" });

        Prices = prices;

    }
}

Answer 1

以下是我的建议：

public void LoadPrices()
{
    // Prices loading...

    Prices = prices;

    foreach (var price in Prices)
    {
        price.PropertyChanged += (s, e) => 
        {
            if (e.PropertyName.Equals(nameof(Price.GivenPrice)))
            {
                // do your WCF call here...
            }
        };
    }
}

注意！如果您要添加/删除价格，您还应该订阅 ObservableCollection 的 CollectionChanged 并手动处理订阅：

Prices.CollectionChanged += (s, e) => 
{
    // Subscribing on property changed event for newly added prices
    if (e.Action == NotifyCollectionChangedAction.Add)
        foreach (Price item in e.NewItems)
            item.PropertyChanged += WCFCallHandler;
    // Unsubscribing from property changed event of removed prices 
    if (e.Action == NotifyCollectionChangedAction.Remove)
        foreach (Price item in e.OldItems)
            item.PropertyChanged -= WCFCallHandler;
};

WPF MVVM - 如何调用外部服务 (WCF) 来更新模型 OnPropertyChanged？

WPF MVVM - How to call external service (WCF) to update model OnPropertyChanged?

c#

wpf

wcf

mvvm