Question

如何将此属性转换为依赖项属性？关于这一点，每个人都只是说“不要在依赖属性中使用逻辑”，并没有提出补救措施：

    public DateTime? SelectedDateGeorgian
    {
        get
        {
           //choose a control based on this "user control" current mode 
           //and return its value
        }


        set
        {
           //choose a control based on this "user control" current mode 
           // and set its property after some manipulations on the value 
        }
    }

我想将其转换为：

    public static readonly DependencyProperty SelectedDateGeorgianProperty =
    DependencyProperty.Register("SelectedDateGeorgian", typeof(DateTime?), typeof(MyDatePicker), new PropertyMetadata(default(DateTime?)));

    public DateTime? SelectedDateGeorgian
    {
        get
        {
            //Its prohobited to do something here ! So what should I do ?
            //How should I select a control and return its value here ?
            //I can't have a simple backing variable because I should do some conversion here                 

            return (DateTime?)GetValue(SelectedDateGeorgianProperty);
        }
        set
        {
             //I want to convert received value here and 
             // and after that update some UI properties in this user control

            SetValue(SelectedDateMiladiProperty, value);
        }
    }

我想转换将在此依赖项属性中写入的值，并且还要更新UIElements。

此外，我还希望从UIElement转换一个值，并在每次读取时返回转换后的值。

所以你看到我不能有一个简单的支持变量。

请有人给我一个模式来实现这个。

感谢您的关注。

Answer 1

是的，你可以。

您必须将UIElement property绑定到此DependencyProperty并使用Converter。请参阅How to: Convert Bound Data。

BTW：Here你可以找到原因，为什么DependencyProperties在属性包装器中不应该有其他逻辑。

修改

<DatePicker Name="dp1" SelectedDate="{Binding Path=SelectedDateGeorgian, RelativeSource="{RelativeSource AncestorType=UserControl}"}" /> <DatePicker Name="dp2" SelectedDate="{Binding Path=SelectedDateGeorgian, RelativeSource="{RelativeSource AncestorType=UserControl}", Converter={StaticResource dateConverter}}" />

创建转换器：

[ValueConversion(typeof(DateTime?), typeof(DateTime?))] public class DateConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { // your conversions } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { // your backconversions } }

并将其添加为资源：

<src:DateConverter x:Key="dateConverter"/>

如何向依赖属性添加逻辑？

1 个答案: