c# - WPF 样式 setter 不工作

Question

我有一个包含组合框的自定义用户控件。我添加了一个 ComboBoxWidth 依赖属性，以允许开发人员根据需要设置宽度。使用样式 setter ，我想将所有这些组合框的宽度设置为另一个用户控件上的相同值，以保持大小一致性。但是，它不起作用。如果我在每个控件上分别设置大小，它就会起作用。当在样式 setter 中指定尺寸时，它会被忽略。如果我将属性字符串从“ComboBoxWidth”更改为“Width”，所有控件的整个宽度都会更改。所以，看起来样式格式是正确的。我错过了什么吗？这是我第一次尝试将样式应用于我自己的自定义依赖项属性。

注意:AngleUserControl 基于通用用户控件(不包括在代码中创建的任何 xaml 控件)。 ComboBoxWidth 属性位于通用基类中。我不确定这是否与此有关。

样式代码(在包含多个 AngleUserControl 控件的用户控件中):

<UserControl.Resources>
    <Style TargetType="wpfControls:AngleUserControl">
        <Setter Property="ComboBoxWidth" Value="400"/>
    </Style>
</UserControl.Resources>

单位控制基地:

/// <summary>
/// Control that displays value in different units depending on selected unit type.
/// </summary>
/// <typeparam name="TSelectionTypeEnum">The enumeration type for all the available units.</typeparam>
/// <typeparam name="TConverterType">The MultiValueConverter that converts the value between the different types of units.</typeparam>
/// <typeparam name="TValueType">The underlying type of the stored value.</typeparam>
public class UnitControlBase<TSelectionTypeEnum, TConverterType, TValueType> : UserControl
    where TSelectionTypeEnum : struct, IConvertible
    where TConverterType : IMultiValueConverter, new()
{
    #region Private Fields

    // Metadata for the dependency properties.
    private static FrameworkPropertyMetadata valuePropertyMetadata = new FrameworkPropertyMetadata(default(TValueType));
    private static FrameworkPropertyMetadata valueTypePropertyMetadata = new FrameworkPropertyMetadata(default(TSelectionTypeEnum));
    private static FrameworkPropertyMetadata displayValueTypePropertyMetadata = new FrameworkPropertyMetadata(default(TSelectionTypeEnum));
    private static FrameworkPropertyMetadata comboBoxWidthPropertyMetadata = new FrameworkPropertyMetadata(0.0);
    private static FrameworkPropertyMetadata valueFormatPropertyMetadata = new FrameworkPropertyMetadata(string.Empty);

    #endregion

    #region Constructor

    /// <summary>
    /// Constructor
    /// </summary>
    public UnitControlBase()
    {
        ValueFormat = "#,##0.00";
        ComboBoxWidth = 75.0;

        // Create main grid and add to control.
        Grid mainGrid = new Grid();
        mainGrid.Name = "LayoutRoot";
        this.AddChild(mainGrid);

        // Create grid columns.
        ColumnDefinition col1 = new ColumnDefinition();
        col1.Width = GridLength.Auto;
        ColumnDefinition col2 = new ColumnDefinition();
        mainGrid.ColumnDefinitions.Add(col1);
        mainGrid.ColumnDefinitions.Add(col2);

        // Create the text box that will display the value.
        Label displayValueLabel = new Label();
        displayValueLabel.Name = "DisplayValueLabel";
        Grid.SetColumn(displayValueLabel, 0);
        mainGrid.Children.Add(displayValueLabel);

        // Bind to the multi-value converter that will convert between the types.
        MultiBinding mb = new MultiBinding();
        mb.Converter = new TConverterType();
        mb.Bindings.Add(new Binding("Value") { Source = this });
        mb.Bindings.Add(new Binding("ValueType") { Source = this });
        mb.Bindings.Add(new Binding("DisplayValueType") { Source = this });
        mb.Bindings.Add(new Binding("ValueFormat") { Source = this });
        displayValueLabel.SetBinding(Label.ContentProperty, mb);
        displayValueLabel.HorizontalContentAlignment = System.Windows.HorizontalAlignment.Right;            

        // Create the combo box that will display selected unit.
        ComboBox displayValueComboBox = new ComboBox();
        displayValueComboBox.Name = "DisplayValueComboBox";
        displayValueComboBox.SetBinding(ComboBox.WidthProperty, new Binding("ComboBoxWidth") { Source = this });
        Grid.SetColumn(displayValueComboBox, 1);
        mainGrid.Children.Add(displayValueComboBox);

        // Bind available units and selected units.
        displayValueComboBox.ItemsSource = Enum.GetValues(typeof(TSelectionTypeEnum));
        displayValueComboBox.SetBinding(ComboBox.SelectedItemProperty, new Binding("DisplayValueType") { Source = this });
    }

    #endregion

    #region Dependency Properties

    /// <summary>
    /// Value Dependency Property
    /// </summary>
    public static readonly DependencyProperty ValueProperty =
        DependencyProperty.Register("Value", typeof(TValueType), typeof(UnitControlBase<TSelectionTypeEnum, TConverterType, TValueType>), valuePropertyMetadata);

    /// <summary>
    /// Value Type Dependency Property
    /// </summary>
    public static readonly DependencyProperty ValueTypeProperty =
        DependencyProperty.Register("ValueType", typeof(TSelectionTypeEnum), typeof(UnitControlBase<TSelectionTypeEnum, TConverterType, TValueType>), valueTypePropertyMetadata);

    /// <summary>
    /// Display Value Type Dependency Property
    /// </summary>
    public static readonly DependencyProperty DisplayValueTypeProperty =
        DependencyProperty.Register("DisplayValueType", typeof(TSelectionTypeEnum), typeof(UnitControlBase<TSelectionTypeEnum, TConverterType, TValueType>), displayValueTypePropertyMetadata);

    /// <summary>
    /// Combo Box Width Dependency Property
    /// </summary>
    public static readonly DependencyProperty ComboBoxWidthProperty =
        DependencyProperty.Register("ComboBoxWidth", typeof(double), typeof(UnitControlBase<TSelectionTypeEnum, TConverterType, TValueType>), comboBoxWidthPropertyMetadata);

    /// <summary>
    /// Value Format Dependency Property
    /// </summary>
    public static readonly DependencyProperty ValueFormatProperty =
        DependencyProperty.Register("ValueFormat", typeof(string), typeof(UnitControlBase<TSelectionTypeEnum, TConverterType, TValueType>), valueFormatPropertyMetadata);

    #endregion

    #region Public Properties

    /// <summary>
    /// The underlying stored value.
    /// </summary>
    public TValueType Value
    {
        get
        {
            return (TValueType)GetValue(ValueProperty);
        }
        set
        {
            SetValue(ValueProperty, value);
        }
    }

    /// <summary>
    /// The unit type for the underlying stored value.
    /// </summary>
    public TSelectionTypeEnum ValueType
    {
        get
        {
            return (TSelectionTypeEnum)GetValue(ValueTypeProperty);
        }
        set
        {
            SetValue(ValueProperty, value);
        }
    }

    /// <summary>
    /// The unit type for the displayed value.
    /// </summary>
    public TSelectionTypeEnum DisplayValueType
    {
        get
        {
            return (TSelectionTypeEnum)GetValue(DisplayValueTypeProperty);
        }
        set
        {
            SetValue(DisplayValueTypeProperty, value);
        }
    }

    /// <summary>
    /// Width of combo box displaying available units.
    /// </summary>
    public double ComboBoxWidth
    {
        get
        {
            return (double)GetValue(ComboBoxWidthProperty);
        }
        set
        {
            SetValue(ComboBoxWidthProperty, value);
        }
    }

    /// <summary>
    /// The format of the displayed value.
    /// </summary>
    public string ValueFormat
    {
        get
        {
            return (string)GetValue(ValueFormatProperty);
        }
        set
        {
            SetValue(ValueFormatProperty, value);
        }
    }

    #endregion
}

AngleUserControl.cs

/// <summary>
/// Control allowing user to display a value in degrees, radians, or semicircles.
/// </summary>
public class AngleUserControl : UnitControlBase<AngleSelectionType, AngleMultiValueConverter, double>
{
    #region Constructor

    /// <summary>
    /// Constructor.
    /// </summary>
    public AngleUserControl()
    {
        this.ComboBoxWidth = 175.0;
    }

    #endregion
}

Answer 1

依赖属性的所谓“本地值”，例如

this.ComboBoxWidth = 175.0;

具有比来自 Style Setter 的值更高的值优先级，例如

<Setter Property="ComboBoxWidth" Value="400"/>

因此 Style Setter 无效。

您应该通过覆盖依赖属性元数据来分配一个新的默认值:

public class AngleUserControl : ...
{
    static AngleUserControl()
    {
        ComboBoxWidthProperty.OverrideMetadata(
            typeof(AngleUserControl),
            new PropertyMetadata(175d));
    }
}

参见 Dependency Property Value Precedence供引用。