自定義依賴屬性綁定

Question

我遇到了自定義依賴項屬性綁定的問題。 我們有：自定義用戶控件，具有一個依賴屬性並綁定到self：

<UserControl x:Class="WpfApplication1.SomeUserControl"
         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="300" d:DesignWidth="300" DataContext="{Binding RelativeSource={RelativeSource Mode=Self}}">
<Grid>
    <Label>
        <Label.Template>
            <ControlTemplate>
                <Label Content="{Binding MyTest}"/>
            </ControlTemplate>
        </Label.Template>
    </Label>
</Grid>

......和控制代碼：

public partial class SomeUserControl : UserControl
{
    public SomeUserControl()
    {
        InitializeComponent();
    }

    public static readonly DependencyProperty MyTestProperty = DependencyProperty.Register("MyTest", typeof(int), typeof(SomeUserControl));

    public int MyTest
    {
        get { return (int)GetValue(MyTestProperty); }
        set { SetValue(MyTestProperty, value); }
    }
}

我嘗試使用此控件綁定到簡單模型類的一些簡單屬性：

<UserControl x:Class="WpfApplication1.AnotherUserControl"
         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:wpfApplication1="clr-namespace:WpfApplication1"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300" DataContext="{Binding RelativeSource={RelativeSource Mode=Self}}">
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition Width="Auto"/>
    </Grid.ColumnDefinitions>
    <wpfApplication1:SomeUserControl MyTest="{Binding Path=Model.MyNum}" Grid.Column="0"/>
    <Label Content="{Binding Path=Model.MyNum}" Grid.Column="1"/>
</Grid>

......用代碼

public partial class AnotherUserControl : UserControl
{
    public MyModel Model { get; set; }
    public AnotherUserControl()
    {
        Model = new MyModel();
        Model.MyNum = 1231;
        InitializeComponent();
    }
}

......和型號：

public class MyModel:INotifyPropertyChanged
{
    private int _myNum;

    public int MyNum
    {
        get { return _myNum; }
        set { _myNum = value; OnPropertyChanged("MyNum");}
    }

    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
    }
}

但綁定不起作用。 堆棧在編譯時沒有錯誤。 現在，綁定使用statndart wpf標簽控件（使用相同的模型），並且不使用我的自定義控件和自定義屬性。 請幫我理解這個問題的原因並解決它; 謝謝）

Answer 1

您應該在SomeUserControl使用ElementName Binding。

<UserControl x:Class="WpfApplication1.SomeUserControl"
     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="300" d:DesignWidth="300" 
     x:Name="uc">

<Grid>
    <Label>
        <Label.Template>
            <ControlTemplate>
                <Label Content="{Binding MyTest, ElementName=uc}"/>
            </ControlTemplate>
        </Label.Template>
    </Label>
</Grid>

這里有一些更多信息，為什么你不應該將usercontrol的datacontext設置為self / this。 WPF用戶控件中的數據綁定

Answer 2

您將需要更新您的綁定，如下所示，您必須使用RelativeSource綁定到祖先usercontrol屬性，因為您正在顯式設置子usercontrol的DataContext，默認綁定將搜索子userControl的DataContext內的路徑。

        <wpfApplication1:SomeUserControl MyTest="{Binding Path=DataContext.Model.MyNum, RelativeSource={RelativeSource FindAncestor={x:Type UserControl}}}" Grid.Column="0"/>