c# - 类的新实例中的属性和先前创建的同一类实例中的属性被引用相同的内存

Question

// Interface 
public interface IItem
{
    Collection Collection
    {
        get;
        set;
    }
}

public class Collection : BindableObject
{
    public static readonly BindableProperty ItemsProperty =
        BindableProperty.Create("Items", typeof(ObservableCollection<People>), typeof(Collection), new ObservableCollection<People>(), BindingMode.TwoWay, null, null);
    public ObservableCollection<People> Items
    {
        get { return (ObservableCollection<People>)GetValue(ItemsProperty); }
        set { this.SetValue(ItemsProperty, value); }
    }
}

//Model class.
public class People
{
    public string Name
    {
        get;
        set;
    }
}


//Core logic implementation.
public class SourceItems :BindableObject, IItem
{
    public static readonly BindableProperty CollectionProperty =
        BindableProperty.Create("Collection", typeof(Collection), typeof(SourceItems), new Collection(), BindingMode.TwoWay, null, null);

    public Collection Collection
    {
        get { return (Collection)GetValue(CollectionProperty); }
        set { this.SetValue(CollectionProperty, value); }
    }
}


Public class MainPage()
{
        var firstsource = new SourceItems();
        firstsource.Collection.Items.Add(new People() { Name= "People1" });
        firstsource.Collection.Items.Add(new People() { Name = "People2" });
        firstsource.Collection.Items.Add(new People() { Name = "People3" });

        var secondSource = new SourceItems();
        secondSource.Collection.Items.Add(new People() { Name = "People4" });
        secondSource.Collection.Items.Add(new People() { Name = "People5" });
        secondSource.Collection.Items.Add(new People() { Name = "People6" });
}

在这里，我在执行上述代码实例后为类“SourceItems”创建了两个不同的对象，firstsource.Collection.Items 包含 6 个项目，而 secondSource.Collection.Items 也包含相同的 6 个项目。它应该是 3。

请澄清我做错了什么。

我在调试时显示了两个实例值。

Answer 1

firstsource和在您的secondSource代码中不同，而firstsource.Collection与secondSource.Collection.

因为当您对or执行set/getmethod( add new items) 时，它们都指向 ，它是一个静态属性，因此它在他的回答中提到的所有 SourceItems 实例中共享。firstsource.CollectionsecondSource.Collectionpublic static readonly BindableProperty CollectionPropertyJeppe Stig Nielsen

这就是为什么firstsource.Collection.Items拥有 6 个项目并且secondSource.Collection.Items还拥有相同的 6 个项目。它们是同一个集合。

Answer 2

您面临的问题是您使用new ObservableCollection<People>()默认值。这意味着每个实例都将使用相同的实例。new ObservableCollection<People>()是唯一执行的。

您可以为 Collection 属性分配一个新的 ObservableCollection

var firstsource = new SourceItems();
firstsource.Collection = new ObservableCollection<People>();

或者

public class Collection : BindableObject
{
    public static readonly BindableProperty ItemsProperty =
        BindableProperty.Create("Items", typeof(ObservableCollection<People>), typeof(Collection), null, BindingMode.TwoWay, null, null);
    public ObservableCollection<People> Items
    {
        get { return (ObservableCollection<People>)GetValue(ItemsProperty); }
        set { this.SetValue(ItemsProperty, value); }
    } = new ObservableCollection<People>();
} 

或者使用构造函数。

Answer 3

您CollectionProperty是一个static字段，因此所有实例之间共享同一个SourceItems实例。