Question

我有一个课程如下

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
}

此类在单独的程序集中编译。然后我将它添加到我的MainWindow构造函数中，如下所示[edit]

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

[结束编辑] 在我的XMAL中，我有[编辑]

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

[结束编辑] 问题是我的Configuration类的“PropertyChanged”成员始终设置为null。我哪里错了？

Answer 1

问题是你的CurrentConfig太晚了：

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

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

我怀疑你想改变这个：

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

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

此外，您的绑定设置为Source=CurrentConfiguration，但您的媒体资源名称似乎为CurrentConfig。您可能需要调整数据上下文或绑定路径。将DataContext设置为显示后，您可以删除源，因为您希望绑定绑定到自身。

Answer 2

Source=CurrentConfiguration将Source设置为字符串"CurrentConfiguration"，显然不具备该属性。

Debug your binding和see the references如果你对它们不够了解的话。

Answer 3

删除空检查。当您通常实现INotifyProperty时，不要检查它。

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

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

INotifyPropertyChanged的PropertyChanged成员始终为null

3 个答案: