如何防止属性的无限变化

当需要跨多个属性进行流量控制时，我将建立一个流量控制变量-一个布尔值-并且在每个正在更改的属性中，我将添加一个测试来查看我是否处于流量控制之下。

private bool controlledChange = false;
public property int MyVal1
{
    set 
    {
        _myVal1 = value;
        if(!controlledChange)
        {
            controlledChange = true;
            MyVal2 -= 1;
            controlledChange = false;
        }
    }
}
public property int MyVal2
{
    set 
    {
        _myVal2 = value;
        if(!controlledChange)
        {
            controlledChange = true;
            MyVal1 += 1;
            controlledChange = false;
        }
    }
}

这样，无论属性发生了什么变化，都可以启动其他属性的变化，但是当它们发生变化时，它们将不会依次启动它们自己的一组变化。

如果这些属性可以产生计算结果，那么您还应该尽可能多地将这些属性设置为只读，以便限制对象的更改方式。

最简单的方法是仅在属性确实发生更改时引发更改事件:

public decimal SalePrice {
   get{
       return salePrice;
   }
   set {
        if (salePrice != value) {
          salePrice = value; // putting as first statement prevents the setter 
                             // to be entered again ...
          RaiseSalePriceChange();
          // Set other properties
        }
   }
}

我不确定我完全理解，因为我不知道你说的"无限"是什么意思

这可能是一个用字段支持属性的好用例。这样，您就可以在属性集上触发事件，但在内部一次只设置一个字段，而不会触发N个事件。

class MyClass
{
    private string m_Name;
    private int m_SomeValue;
    public string Name
    {
        get { return m_Name; }
        set
        {
            if (value != m_Name)
            {
                m_Name = value;
                m_SomeValue++;
                // Raise Event
            }
        }
    }
    public int SomeValue
    {
        get { return m_SomeValue; }
        set
        {
            if (m_SomeValue != value)
            {
                m_SomeValue = value;
                // Raise Event
            }
        }
    }

如果INotifyPropertyChanged确实需要通知外部对象，那么我将只集中所有内容。这样的:

    private double salesPrice;
    private double downPaymentAmount;
    private double downPaymentPercent;
    private double loanAmount;
    public double SalesPrice
    {
        get
        {
            return salesPrice;
        }
        set
        {
            if (salesPrice != value)
            {
                salesPrice = value;
                // maybe you would rather use a RecalculateForSalePriceChanged() method
                RecalculateDownPaymentAmount();
                RecalculateDownPaymentPercent();
                RecalculateLoanAmount();
                propertiesChanged();
            }
        }
    }
    public double DownPaymentAmount
    {
        get
        {
            return downPaymentAmount;
        }
        set
        {
            if (downPaymentAmount != value)
            {
                downPaymentAmount = value;
                // see above
                RecalculateDownPaymentPercent();
                RecalculateLoanAmount();
                RecalculateSalesPrice();
                propertiesChanged();
            }
        }
    }
    public double DownPaymentPercent
    {
        get
        {
            return downPaymentPercent;
        }
        set
        {
            if (downPaymentPercent != value)
            {
                downPaymentPercent = value;
                // see above
                RecalculateDownPaymentAmount();
                RecalculateLoanAmount();
                RecalculateSalesPrice();
                propertiesChanged();
            }
        }
    }
    public double LoanAmount
    {
        get
        {
            return loanAmount;
        }
        set
        {
            if (loanAmount != value)
            {
                loanAmount = value;
                // see above
                RecalculateDownPaymentAmount();
                RecalculateDownPaymentPercent();
                RecalculateSalesPrice();
                propertiesChanged();
            }
        }
    }
    private void propertiesChanged()
    {
        RaisePropertyChanged("SalesPrice", "DownPaymentAmount", "DownPaymentPercent", "LoanAmount");
    }

也许你可以集中在更少的方法，甚至一个单一的重新计算，但我不知道你是如何计算他们。但是，在重新计算这些值时，必须保持特定的顺序。因为它们只操作字段而不改变属性，所以不会有propertychanged -feedback循环。

希望这对你有帮助，我没有误解你想要的。

OP想要的是如下内容

class A : INotifyPropertyChanged
{
    private int field1;
    public int Property1
    {
        get { return field1; }
        set
        {
            field1 = value;
            field2++;
            RaisePropertyChanged("Property1");
            RaisePropertyChanged("Property2");
        }
    }
    private int field2;
    public int Property2
    {
        get { return field2; }
        set
        {
            field2 = value;
            field1++;
            RaisePropertyChanged("Property1");
            RaisePropertyChanged("Property2");
        }
    }
    public event PropertyChangedEventHandler PropertyChanged;
    private void RaisePropertyChanged(string propertyName)
    {
        var handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

他可能正在处理他提到的每个属性的setter中的其他属性，从而导致循环调用setter。

Vijay