通知一个对象时的另一个对象的属性发生更改 [英] Notify One object when a property of another object changes

问题描述

我有一个父对象调用页面，有对象的列表，名为控制：

 公共类页
{
   名单＆LT; CustomControl＆GT;控制{获取;集;}
}
 

该CustomControl类具有以下确定指标：

 公共类CustomControl
{
 字符串名称{获取;集;}
 字符串值{获取;集;}
}
 

例如说Page类有两个CustomControls A和B是否有可能通知自定​​义控件B计算的自定义控件的属性值更改，以便它可以改变它的一些属性。

我在想，现在执行的CustomControl类INotifyPropertyChanged的事件我怎么通知CustomControl的实例时同一个类的其他实例有其修改了一些属性。

解决方案

 公共类CustomControl：INotifyPropertyChanged的
{
    私人字符串_name;
    公共字符串名称
    {
        {返回_name; }
        组
        {
            如果（_name ==值）回报;
            _name =价值;
            的PropertyChanged（这一点，新PropertyChangedEventArgs（名称））;
        }
    }

    私人字符串_value;
    公共字符串值
    {
        得到{_value; }
        组
        {
            如果（_value ==值）回报;

            _value =值;
            的PropertyChanged（这一点，新PropertyChangedEventArgs（值））;
        }
    }

    公共事件PropertyChangedEventHandler的PropertyChanged =委托{};

    内部虚拟无效OnSiblingInPagePropertyChanged（对象发件人，PropertyChangedEventArgs参数）
    {

    }
}

公共类CustomControlObservableColletion：的ObservableCollection＆LT; CustomControl＆GT;
{
    //必需的，因为，在默认情况下，这是不可能找出哪些项目
    //已被清除时，CollectionChanged事件.Clear（）调用之后被激发。
    保护覆盖无效ClearItems（）
    {
        的foreach（在Items.ToList VAR项目（））
            删除（项目）;
    }

}

公共类页
{
    公众的IList＆LT; CustomControl＆GT;控制{获得;私定; }

    公共页面（）
    {
        无功控制=新CustomControlObservableColletion（）;
        controls.CollectionChanged + = OnCollectionChanged;
        控制=控制;
    }

    私人无效OnCollectionChanged（对象发件人，NotifyCollectionChangedEventArgs E）
    {
        开关（e.Action）
        {
            案例NotifyCollectionChangedAction.Add：
                RegisterControls（e.NewItems）;
                打破;

            案例NotifyCollectionChangedAction.Replace：
                RegisterControls（e.NewItems）;
                DeRegisterControls（e.OldItems）;
                打破;

            案例NotifyCollectionChangedAction.Remove：
                DeRegisterControls（e.OldItems）;
                打破;
        }
    }

    私人无效RegisterControls（IList的控制）
    {
        的foreach（对照CustomControl控制）
            control.PropertyChanged + = OnControlPropertyChanged;
    }

    私人无效DeRegisterControls（IList的控制）
    {
        的foreach（对照CustomControl控制）
            control.PropertyChanged  -  = OnControlPropertyChanged;
    }

    私人无效OnControlPropertyChanged（对象发件人，PropertyChangedEventArgs E）
    {
        的foreach（在Controls.Where功控制（C =＆GT;！C =发送者））
            control.OnSiblingInPagePropertyChanged（发件人，E）;
    }
}
 

I have a parent object called Page that has a List of objects called Control:

public class Page
{
   List<CustomControl> controls {get;set;}
}

The CustomControl class has the following defintion:

public class CustomControl
{
 string Name {get;set;}
 string Value {get;set;}
}

Say for instance the Page class has two CustomControls A and B. Is it possible to Notify Custom Control B when the property Value of Custom Control A changes so that it can change some of its properties.

I was thinking of implementing the INotifyPropertyChanged event on the CustomControl class now how do I notify an instance of the CustomControl when another instance of the same class has some property of its Modified.

解决方案

public class CustomControl : INotifyPropertyChanged
{
    private string _name;
    public string Name
    {
        get { return _name; }
        set
        {
            if (_name == value) return;
            _name = value;
            PropertyChanged(this, new PropertyChangedEventArgs("Name"));
        }
    }

    private string _value;
    public string Value
    {
        get { return _value; }
        set
        {
            if (_value == value) return;

            _value = value;
            PropertyChanged(this, new PropertyChangedEventArgs("Value"));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged = delegate { };

    internal virtual void OnSiblingInPagePropertyChanged(object sender, PropertyChangedEventArgs args)
    {

    }
}

public class CustomControlObservableColletion : ObservableCollection<CustomControl>
{
    // Required because, by default, it is not possible to find out which items
    // have been cleared when the CollectionChanged event is fired after a .Clear() call.
    protected override void ClearItems()
    {
        foreach (var item in Items.ToList())
            Remove(item);
    }

}

public class Page
{
    public IList<CustomControl> Controls { get; private set; }

    public Page()
    {
        var controls = new CustomControlObservableColletion();
        controls.CollectionChanged += OnCollectionChanged;
        Controls = controls;
    }

    private void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        switch (e.Action)
        {
            case NotifyCollectionChangedAction.Add:
                RegisterControls(e.NewItems);
                break;

            case NotifyCollectionChangedAction.Replace:
                RegisterControls(e.NewItems);
                DeRegisterControls(e.OldItems);
                break;

            case NotifyCollectionChangedAction.Remove:
                DeRegisterControls(e.OldItems);
                break;
        }
    }

    private void RegisterControls(IList controls)
    {
        foreach (CustomControl control in controls)
            control.PropertyChanged += OnControlPropertyChanged;
    }

    private void DeRegisterControls(IList controls)
    {
        foreach (CustomControl control in controls)
            control.PropertyChanged -= OnControlPropertyChanged;
    }

    private void OnControlPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        foreach (var control in Controls.Where(c => c != sender))
            control.OnSiblingInPagePropertyChanged(sender, e);
    }
}

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