INotifyPropertyChanged的PropertyChanged成员始终为null

Question

I have a class as follows

public partial class Configuration : INotifyPropertyChanged
{
    private bool _isToolTips;
    public bool IsToolTips
    {
        get { return _isToolTips; }
        set { Set(this, "IsToolTips", ref _isToolTips, value, PropertyChanged); }
    }

    #region INotifyPropertyChanged functionality

    public static void Set<T>(object owner, string propName, ref T oldValue, T newValue,
        PropertyChangedEventHandler eventHandler)
    {
        // make sure the property name really exists
        if (owner.GetType().GetProperty(propName) == null)
        {
            throw new ArgumentException("No property named ‘" +
                propName + "‘ on " + owner.GetType().FullName);
        }

        // we only raise an event if the value has changed
        if (Equals(oldValue, newValue)) return;
        oldValue = newValue;
        if (eventHandler != null)
        {
            eventHandler(owner, new PropertyChangedEventArgs(propName));
        }
    }
    public event PropertyChangedEventHandler PropertyChanged;
    private void notifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    #endregion INotifyPropertyChanged functionality
}

This class is compiled in a separate assembly. I then add it to my MainWindow constructor as follows [edit]

    public MainWindow()
    {
        initializeAttributes();
        InitializeComponent();
        CurrentConfig = new Configuration
        {
            IsToolTips = true
        };
        DataContext = CurrentConfig;
        composeModules();
    }

[end edit] and in my XMAL I have this [edit]

<MenuItem Name="ToolTips"
    Header="Tool Tips"
    IsCheckable="True"
    IsChecked="{Binding Source=CurrentConfig,
                        Path=IsToolTips,
                        Mode=TwoWay}"
    Click="onToolTipsClick">
</MenuItem>

[end edit] The problem is that the "PropertyChanged" member of my Configuration class is always set to null. Where am I going wrong?

Answer 1

The problem is that you're initializing your CurrentConfig too late:

// Setting data context here...
DataContext = CurrentConfig;
InitializeComponent();

// This makes a new instance, but does not update the data context!
CurrentConfig = new Configuration
    {
        IsToolTips = true
    };

I suspect you want to change this around:

InitializeComponent();    
CurrentConfig = new Configuration
    {
        IsToolTips = true
    };

// Set this AFTER you construct your CurrentConfig
DataContext = CurrentConfig;

Also, your binding is setup with Source=CurrentConfiguration , but your property name seems to be CurrentConfig . You may need to adjust your data context or binding path. With the DataContext set as displayed, you can likely remove the source, as you want the binding to bind to itself.

Answer 2

Source=CurrentConfiguration sets the Source to the string "CurrentConfiguration" , which obviously won't have that property.

Debug your binding and see the references if you don't know enough about them.

Answer 3

Remove the null check. When you normally implement an INotifyProperty you don't check for it.

public string _PhoneNumber
public string PhoneNumber
{
    get
    {
        return _PhoneNumber;
    }

    set
    {
        if (value != PhoneNumber)
        {
            _PhoneNumber = value;
            NotifyPropertyChanged("PhoneNumber");
        }
    }
}