class 中使用合成的 MvvmLight

Question

我有一个 ViewModel，派生自 MvvmLight.ViewModelBase，它使用组合来重用其他类:

我想在合成中重复使用的类的简化版本：

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

    public ITimeFrame CreateTimeFrame() {...}
}

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

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

我的 ViewModel 派生自 MvvmLight ViewModelBase 是这两者的组合：

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);
    }
}

Get/Set 与字段一起工作，但如果我想将属性转发到复合对象，我不能使用 base.Set

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

属性不允许引用。

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));
        }
    }

如果您必须为很多属性执行此操作，那就太麻烦了。有没有一种巧妙的方法可以做到这一点，可能类似于 ObservableObject.Set?

Answer 1

嗯，基本方法需要能够读取（用于比较）和写入传递的 field/property，因此引用

由于您不能通过引用传递属性，我认为您被迫编写了另一个基本方法

A) 获得 getter/setter 代表。（冗长/烦人）

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

或

B) 传递一个包含属性的 Expression<Func<T>> 并使用反射在基础中提取属性和 get/set 它（慢，但可能会提取名称也是）

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

class 中使用合成的 MvvmLight

MvvmLight in a class that uses composition

c#

mvvm

mvvm-light

observablecollection