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我创建了一个自定义控件，它只是三个单选按钮，以及一个可以是 、 或 之一的类型Answer属性。单击单选按钮会更改属性，或者更改属性应该会更改选择了哪个单选按钮。被实现为 DependancyProperty，因此我可以使用它执行数据绑定（源是 EF4 实体的属性）。string"Yes""No""N/A"AnswerAnswerAnswer

这一切都很好，除了在一种特殊情况下 - 当数据库中列的值与DependencyProperty.Register()调用中指定的默认值匹配时。在这种情况下，控件显示时没有选中任何单选按钮！

我已经关闭了调试器跳过属性设置器的选项，并且我知道SetChecks() 正在被调用，并且应该将IsChecked单选按钮的属性设置为 true。

如果我更改属性的默认值，则该值将变为未检查的值……MyId只是为了识别我在调试器中查看的特定控件，因为我的视图中有多个这些控件。

首先是.cs代码：

public partial class YesNoNotApplicableRadio : UserControl, INotifyPropertyChanged {
    public string MyId {
        get;
        set;
    }

    public static readonly DependencyProperty AnswerProperty = DependencyProperty.Register(
        "Answer",
        typeof(string),
        typeof(YesNoNotApplicableRadio),
        new FrameworkPropertyMetadata("N/A",
            FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
            new PropertyChangedCallback(AnswerPropertyChanged),
            new CoerceValueCallback(CoerceAnswer)
            ),
        new ValidateValueCallback(ValidateAnswer)
        );

    public static bool ValidateAnswer(Object value) {
        string s = value as string;
        if (s == null)
            return true;
        s = s.Trim().ToUpper();
        if (s.Equals("YES") || s.Equals("NO") || s.Equals("N/A") || s.Equals(""))
            return true;
        return false;
    }

    public static void AnswerPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
        YesNoNotApplicableRadio o = d as YesNoNotApplicableRadio;
        string val = (string)e.NewValue;
        SetChecks(o, val.Trim().ToUpper());
    }

    private static void SetChecks(YesNoNotApplicableRadio selector, string val) {
        selector.YesRadio.IsChecked = false;
        selector.NoRadio.IsChecked = false;
        selector.NaRadio.IsChecked = false;
        if (val.Equals("YES"))
            selector.YesRadio.IsChecked = true;
        else if (val.Equals("NO"))
            selector.NoRadio.IsChecked = true;
        else if (val.Equals("N/A") || val.Equals(""))
            selector.NaRadio.IsChecked = true;
    }

    private void Radio_Click(object sender, RoutedEventArgs e) {
        if ((bool)YesRadio.IsChecked)
            Answer = "Yes";
        else if ((bool)NoRadio.IsChecked)
            Answer = "No";
        else
            Answer = "N/A";
    }

    public static Object CoerceAnswer(DependencyObject d, Object baseValue) {
        YesNoNotApplicableRadio o = (YesNoNotApplicableRadio)d;
        string s = baseValue as string;
        if (s == null)
            return ("N/A");
        else
            return (s);
    }

    public string Answer {
        get { return ((string)GetValue(AnswerProperty)); }
        set { SetValue(AnswerProperty, value); NotifyPropertyChanged("Answer"); }
    }

    public YesNoNotApplicableRadio() {
        InitializeComponent();
        Guid groupGuid = System.Guid.NewGuid();
        YesRadio.GroupName = groupGuid.ToString();
        NoRadio.GroupName = groupGuid.ToString();
        NaRadio.GroupName = groupGuid.ToString();

    }

    public event PropertyChangedEventHandler PropertyChanged;

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

这是.xaml：

<UserControl x:Class="RovingAuditEntry.Controls.YesNoNotApplicableRadio"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             mc:Ignorable="d"
             d:DesignHeight="30" d:DesignWidth="130">
    <StackPanel Orientation="Horizontal" Margin="5">
        <RadioButton Content="Yes" Height="16" Name="YesRadio" Click="Radio_Click" />
        <RadioButton Content="No" Height="16" Name="NoRadio" Margin="5,0,0,0" Click="Radio_Click" />
        <RadioButton Content="N/A" Height="16" Name="NaRadio" Margin="5,0,0,0" Click="Radio_Click" />
    </StackPanel>
</UserControl>
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1 回答 1

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我想出了一个解决方案，尽管它可能不是正确的。控件的有效输入是null、空字符串、"Yes"、"No"和"N/A"（任意大小写）。我的强制函数将转换null并将空字符串转换为"N/A". Register()通过将传递给函数的默认值从 更改"N/A"为""，它现在可以工作了。

仍在寻找更好的答案，但在没有答案的情况下，我会接受自己的答案。

于 2012-12-27T16:05:01.733 回答