Question

我想检查属性是否在不属于我的类中更改，并且未实现INotifyPropertyChanged。这个类是API的一部分，我想在Name属性更改时引发事件。

class SomethingChanged : INotifyPropertyChanged
{
    Something sth;
    string Name { get; set; }
    public SomethingChanged(Something Sth)
    {
        sth = Sth;
        Name = sth.Name;
        //do something to allow raise PropertyChangedEvent when sth.Name changes
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

我想在WPF中使用它（treeView）。有没有办法做到这一点？

如果那个类（上面的例子中的某些内容）没有实现INotifyPropertyChanged，我还是运气不好吗？

Answer 1

不幸的是，由于你的约束，你唯一的选择是poling以查看数据是否已经改变。

sealed class SomethingChanged : INotifyPropertyChanged, IDisposeable
{
    private Something sth;
    private string _oldName;
    private System.Timers.Timer _timer;

    public string Name { get { return sth.Name; }

    public SomethingChanged(Something Sth, double polingInterval)
    {
        sth = Sth;
        _oldName = Name;
        _timer = new System.Timers.Timer();
        _timer.AutoReset = false;
        _timer.Interval = polingInterval;
        _timer.Elapsed += timer_Elapsed;
        _timer.Start();
    }

    private void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    {
        if(_oldName != Name)
        {
           OnPropertyChanged("Name");
           _oldName = Name;
        }

        //because we did _timer.AutoReset = false; we need to manually restart the timer.
        _timer.Start();
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string propertyName)
    {
        var tmp = PropertyChanged; //Adding the temp variable prevents a NullRefrenceException in multithreaded environments.
        if (tmp != null)
            tmp(this, new PropertyChangedEventArgs(propertyName));
    }

    public void Dispose()
    {
        if(_timer != null)
        {
            _timer.Stop();
            _timer.Dispose();
        }
    }
}

当外来类中的属性发生更改时，C＃引发事件

1 个答案: