通过xaml设置用户控件的自定义依赖属性

Question

这是我的用户控件（MonthCal）的代码。

public partial class MonthCal : UserControl
{
    public DayOfWeek StartDayOfWeek { get { return (DayOfWeek)GetValue(StartDayOfWeekProperty); } set { SetValue(StartDayOfWeekProperty, value); } }
    public static readonly DependencyProperty StartDayOfWeekProperty = DependencyProperty.Register("StartDayOfWeek", typeof(DayOfWeek), typeof(MonthCellHeader), new UIPropertyMetadata(DayOfWeek.Sunday, StartDayOfWeek_PropertyChanged));
    //...
}

另外，这是 MonthCal 的 xaml。

<UserControl x:Class="GCDR.MonthCal"
             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">
    <!-- ... -->
</UserControl>

那么，如何在 xaml 中设置“StartDayOfWeek”依赖属性？正如你们所知，以下代码是不可能的：

<UserControl ...
             StartDayOfWeek="Sunday">
</UserControl>

请给我帮助。

Answer 1

您不能在 UserControl 的标记中使用依赖属性，但是当您将用户控件的实例放置在某个位置时可以使用它，如下所示：

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication1">
    <Grid>
        <local:UserControl1 local:StartDayOfWeek="Friday" />
    </Grid>
</Window>

在用户控件中，您可以将一些其他属性绑定到您的依赖属性，如下所示：

<UserControl x:Class="WpfApplication1.UserControl1"
             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" 
             xmlns:local="clr-namespace:WpfApplication1"
             mc:Ignorable="d" >
    <Grid>
        <Label Content="{Binding RelativeSource={RelativeSource AncestorType=local:UserControl1},Path=StartDayOfWeek}"  />
    </Grid>
</UserControl>

Answer 2

为什么不能设置StartDayOfWeek是因为XAML中的UserControl没有StartDayOfWeek依赖属性，换句话说UserControl类型不是MonthCal类型。

由于在XAML中，UserControl是UserControl1的基类，因此您可以定义MonthCal继承UserControl，然后在XAML中声明MonthCal。

XAML

<local:MonthCal x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1" Title="MainWindow"
                Height="350" Width="525"
                StartDayOfWeek="Monday">
    <Grid></Grid>
</local:MonthCal>

代码隐藏

namespace WpfApplication1
{
    public class MonthCal : Window
    {
        public DayOfWeek StartDayOfWeek { get { return (DayOfWeek)GetValue(StartDayOfWeekProperty); } set { SetValue(StartDayOfWeekProperty, value); } }
        public static readonly DependencyProperty StartDayOfWeekProperty = 
            DependencyProperty.Register("StartDayOfWeek", typeof(DayOfWeek), typeof(MonthCal), new UIPropertyMetadata(DayOfWeek.Sunday, StartDayOfWeek_PropertyChanged));

        private static void StartDayOfWeek_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
        }
    }

    public partial class MainWindow : MonthCal
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }
}