c# - 使用合成的类中的MvvmLight

Question

我有一个从MvvmLight.ViewModelBase派生的ViewModel，它使用合成来重用其他类:

我想在合成中重用的类的简化版本:

class TimeFrameFactory
{
    public DateTime SelectedTime {get; set;}

    public ITimeFrame CreateTimeFrame() {...}
}

class GraphFactory
{
     public int GraphWidth {get; set;}

     public IGraph CreateGraph(ITimeframe timeframe) {...}
}

从MvvmLight ViewModelBase派生的My ViewModel由以下两个组成:

class MyViewModel : ViewModelBase
{
    private readonly TimeFrameFactory timeFrameFactory = new TimeFrameFactory();
    private readonly GraphFactory graphFactory = new GraphFactory();

    private Graph graph;

    // standard MVVM light method to get/set a field:
    public Graph Graph
    {
        get => this.Graph;
        private set => base.Set(nameof(Graph), ref graph, value);
    }

    // this one doesn't compile:
    public DateTime SelectedTime 
    {
        get => this.timeFrameFactory.SelectedTime;
        set => base.Set(nameof(SelectedTime), ref timeFrameFactory.SelectedTime, value);
    }

    // this one doesn't compile:
    public int GraphWidth
    {
        get => this.timeFrameFactory.GraphWidth;
        set => base.Set(nameof(GraphWidth), ref timeFrameFactory.GraphWidth, value);
    }

    public void CreateGraph()
    {
        ITimeFrame timeFrame = this.timeFrameFactory.CreateTimeFrame();
        this.Graph = this.GraphFactory.CreateGraph(timeFrame);
    }
}

使用字段获取/设置有效，但是如果我想将属性设置为复合对象，则不能使用 base.Set

set => base.Set(nameof(GraphWidth), ref timeFrameFactory.GraphWidth, value);

不允许在属性上使用ref。

我当然可以写:

    public int GraphWidth
    {
        get => this.timeFrameFactory.GraphWidth;
        set
        {
            base.RaisePropertyChanging(nameof(GraphWidh));
            base.Set(nameof(GraphWidth), ref timeFrameFactory.GraphWidth, value);
            base.RaisePropertyChanged(nameof(GraphWidh));
        }
    }

如果必须对很多属性执行此操作，则很麻烦。有没有一种整洁的方式可以做到这一点，可能类似于 ObservableObject.Set？

Answer 1

好吧，基本方法既需要能够读取(用于比较)又可以写入所传递的字段/属性，从而能够读取引用。

由于您无法通过引用传递属性，因此我认为您不得不编写另一种基本方法，

A)接受getter/setter代表。 (详细/烦人)

public int GraphWidth
{
    get => this.timeFrameFactory.GraphWidth;
    set => base.Set(nameof(GraphWidth), () => timeFrameFactory.GraphWidth, x => timeFrameFactory.GraphWith = x, value);
}

或者

B)传递一个包含该属性的 Expression<Func<T>>，并使用反射来提取该属性并在基础中获取/设置它(慢，但也可能提取名称)

public int GraphWidth
{
    get => this.timeFrameFactory.GraphWidth;
    set => base.Set(() => timeFrameFactory.GraphWidth, value);
}