DependencyProperty默认值

Question

我正在尝试在WPF中使用DependencyProperty.我正在使用:

public static readonly DependencyProperty DisplayModeProperty = DependencyProperty.Register("DisplayMode", typeof (TescoFoodSummary), typeof (Orientation), new UIPropertyMetadata(Orientation.Vertical));
    /// <summary>
    /// Gets or sets the orientation.
    /// </summary>
    /// <value>The orientation.</value>
    public Orientation DisplayMode {
        get { return (Orientation)base.GetValue(DisplayModeProperty); }
        set { base.SetValue(DisplayModeProperty, value); }
    }

当我初始化窗口时,我收到一个错误:默认值类型与属性'DisplayMode'的类型不匹配.但是,如果我保留默认值,则由于未设置DisplayModeProperty而导致窗口加载时,我会得到一个空引用异常.

Answer 1

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根据msdn DependencyProperty.Register方法,语法看起来如此:

public static DependencyProperty Register(
    string name,
    Type propertyType,
    Type ownerType,
    PropertyMetadata typeMetadata
)

在您的情况下,ownerType为TescoFoodSummary和propertyType为Orientation,因此参数具有以下位置:

DependencyProperty.Register("DisplayMode", typeof (Orientation), typeof (TescoFoodSummary), new UIPropertyMetadata(Orientation.Vertical));