Question

我刚刚发现了一个INotifyPropertyChange接口。我设法在我的clss中实现这个接口，一切正常。但是我想知道是否可以在代码中拦截此事件并触发一个函数假设我有一个功能

DoStuff()

每次property1，property2或property3发生变化时，我都不会激活此函数。当然我可以把这个函数放在我班上的set block中，但这不是一个好主意（我认为）。

Answer 1

如果您指的是处理此事件的内部方法，您可以通过在类构造函数中注册事件来实现。例如：

public class AnswerViewModel : IAnswerViewModel
{
    public event PropertyChangedEventHandler PropertyChanged;

    private string content;

    public AnswerViewModel()
    {
        PropertyChanged += (sender, args) => DoStuff();
    }

    public string Content
    {
        get { return content; }
        set
        {
            content = value;
            PropertyChanged(this, new PropertyChangedEventArgs("Content"));
        }
    }

    public void DoStuff()
    {
        // this method will be called whenever PropertyChanged event raised
    }
}

如果拦截方法属于其他类：

public class PropertiesInterceptor
{
    private readonly AnswerViewModel viewModel;

    private readonly List<string> propertiesToIntercept =
        new List<string> { "property1", "property2", "property3" };

    public PropertiesInterceptor(AnswerViewModel viewModel)
    {
        this.viewModel = viewModel;
        viewModel.PropertyChanged += OnPropertyChanged;
    }

    private void OnPropertyChanged(object sender, PropertyChangedEventArgs args)
    {
        if (propertiesToIntercept.Contains(args.PropertyName))
        {
            DoStuff();
        }
    }

    private void DoStuff()
    {
        // Do something with viewModel
    }
}

Answer 2

您是否需要它来替换现有的NotifyPropertyChanged事件处理程序，或者只是在调用NotifyPropertyChanged时调用它？

如果你的意思是第二个，你可以简单地注册一个事件处理程序

修改

您可以添加一个在NotifyPropertyChanged上调用的事件处理程序，检查该属性参数是否等于Property1，Property2或Property3，然后才将它转发给您想要调用的实际函数。

Answer 3

拦截PropertyChanged事件：

http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.propertychanged.aspx

Answer 4

您可以从RaisePropertyChanged（）方法触发该方法：

public int Property1
{
    get { return this.property1; }
    set
    {
        if (this.property1 != value)
        {
            this.property1 = value;
            RaisePropertyChanged("Property1");
        }
    }
}

private void RaisePropertyChanged(string propertyName)
{
     if (PropertyChanged != null)
     {
         PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
     }

     DoStuff(); // Call DoStuff here.
}

Answer 5

窃取Elisha的回答，在Merlyn的回答中回答你的问题

public class AnswerViewModel : IAnswerViewModel
{
    public event PropertyChangedEventHandler PropertyChanged;

    private string property1;
    private string property2;
    private string propertyX;

    public AnswerViewModel()
    {
        PropertyChanged += (sender, args) => 
        {
            if(args.PropertyName == "Property1" || args.PropertyName == "Property2")
                DoStuff();
        }
    }

    public string Property1
    {
        get { return content; }
        set
        {
            property1 = value;
            PropertyChanged(this, new PropertyChangedEventArgs("Property1"));
        }
    }
    public string Property2
    {
        get { return content; }
        set
        {
            property2 = value;
            PropertyChanged(this, new PropertyChangedEventArgs("Property2"));
        }
    }
    public string PropertyX
    {
        get { return content; }
        set
        {
            propertyX = value;
            PropertyChanged(this, new PropertyChangedEventArgs("PropertyX"));
        }
    }

    public void DoStuff()
    {
        // this method will be called whenever PropertyChanged event raised from Property1 or Property2
    }
}

如果DoStuff类是成员，则可以

    private otherClass
    public AnswerViewModel()
    {
        PropertyChanged += (sender, args) => 
        {
            if(args.PropertyName == "Property1" || args.PropertyName == "Property2")
                otherClass.DoStuff();
        }
    }

否则你可以让otherClass在你的主代码中自己注册一个事件。

如何拦截NotifyPropertyChange事件

5 个答案: