如何使用INotifyPropertyChanged更新派生的属性

Question

I have a few properties in a bindingList for a XtratreeList(DevExress) where a child node needs to show a parentnode'e property. I have the following code.

public abstract class ClassBase : INotifyPropertyChanged
{
    protected static int initialId = 0;

    private int id;
    private int parentID;
    private string productName;
    private string productType;
    private string colorProductType;

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

    public int ID
    {
        get { return id; }
        set
        {
            if ( id == value )
                return;

            id = value;
            RaisePropertyChanged("ID");
        }
    }

    public int ParentID
    {
        get { return parentID; }
        set
        {
            if ( parentID == value )
                return;

            parentID = value;
            RaisePropertyChanged("ParentID");
        }
    }

    public string ProductName
    {
        get { return productName; }
        set
        {
            if ( productName == value )
                return;

            productName = value;
            RaisePropertyChanged("ProductName");
        }
    }

    public string ProductType
    {
        get { return productType; }
        set
        {
            if ( productType == value )
                return;

            productType = value;
            RaisePropertyChanged("ProductType");
            RaisePropertyChanged("ColorProductType");
        }
    }

    public string ColorProductType
    {
        get { return colorProductType ; }
        set
        {
            if (colorProductType == value)
                return;

            colorProductType = value;
            RaisePropertyChanged("ColorProductType");
        }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion
}`

My requirement is to have the ColorProductType property changed when the ProductType property changes, basically ProductType is a parent node property and ColorProductType - child's. So on changing the parent's property the child's need to be changed. I have both these properties bound to 2 text boxes. So changing the parent prop should change both textboxes, but the vice versa is not true. RaisePropertyChanged("ColorProductType"); within the parent is not working, colorproducttype is null, what is the issue here?

Answer 1

RaisePropertyChanged does not actually update the property. It simply signals the PropertyChanged event. Something somewhere must subscribe to it and update the other property accordingly. Something like this:

public abstract class ClassBase : INotifyPropertyChanged
{
    private string productType;
    private string colorProductType;

    public ClassBase()
    {
        this.PropertyChanged += HandlePropertyChanged;
    }

    private void HandlePropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if(e.PropertyName == "ProductType")
        {
            // update ColorProductType here
        }
    }

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

    public string ProductType
    {
        get { return productType; }
        set
        {
            if ( productType == value )
                return;

            productType = value;
            RaisePropertyChanged("ProductType");
        }
    }

    public string ColorProductType
    {
        get { return colorProductType ; }
        set
        {
            if (colorProductType == value)
                return;

            colorProductType = value;
            RaisePropertyChanged("ColorProductType");
        }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion
}

Naturally, this is complete overkill. You can update ColorProductType when ProductType is updated and let the PropertyChanged event and databinding handle the textbox update:

public string ProductType
{
    get { return productType; }
    set
    {
        if ( productType == value )
            return;

        productType = value;

        // update ColorProductType here

        RaisePropertyChanged("ProductType");
    }
}