c# - UserControl 与模型的绑定(bind) - "property not found"

Question

我做了一个 super 简单的用户控件来浏览文件

<UserControl x:Class="DrumMapConverter.FileBrowserTextBox"
             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" 
             DataContext="{Binding RelativeSource={RelativeSource Self}}"
             mc:Ignorable="d" Height="24" d:DesignWidth="500">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <TextBlock Grid.Column="0" Name="lblLabel" Text="{Binding Label, Mode=TwoWay}" MinWidth="150"/>
        <Button Grid.Column="1" Content=" ... " Click="BrowseButton_Click"/>
        <TextBox Grid.Column="2" Name="txtFilepath" Text="{Binding FilePath, Mode=TwoWay}"/>
    </Grid>

</UserControl>

具有 2 个依赖属性:

标签和文件路径:

// FilePath
public static readonly DependencyProperty FilePathProperty =
    DependencyProperty.Register("FilePath", typeof(string), typeof(FileBrowserTextBox), new UIPropertyMetadata(string.Empty, new PropertyChangedCallback(OnFilePathPropertyChanged)));

public string FilePath
{
    get { return (string)GetValue(FilePathProperty); }
    set { SetValue(FilePathProperty, value); }
}
static void OnFilePathPropertyChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
    var obj = o as FileBrowserTextBox;
    if (obj == null)
        return;
    FileBrowserTextBox fileBrowserTextBox = (FileBrowserTextBox)o;
    fileBrowserTextBox.txtFilepath.Text = (string)e.NewValue;
}
// Label
public static readonly DependencyProperty LabelProperty =
    DependencyProperty.Register("Label", typeof(string), typeof(FileBrowserTextBox), new UIPropertyMetadata(string.Empty, new PropertyChangedCallback(OnLabelPropertyChanged)));
public string Label
{
    get { return (string)GetValue(LabelProperty); }
    set { SetValue(LabelProperty, value); }
}
static void OnLabelPropertyChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
    var obj = o as FileBrowserTextBox;
    if (obj == null)
        return;
    FileBrowserTextBox fileBrowserTextBox = (FileBrowserTextBox)o;
    fileBrowserTextBox.lblLabel.Text = (string)e.NewValue;
}

然后在我的 MainWindow ctor 中我有这个

private DrumMapConverterDataModel model;
public MainWindow()
{
    InitializeComponent();
    model = new DrumMapConverterDataModel();
    DataContext = model;
}

模型有 2 个属性:

private string inputFile = "";
public string InputFile
{
    get { return inputFile; }
    set { 
        inputFile = value;
        OnPropertyChanged("InputFile");
         }
}

private string outputFile = "";
public string OutputFile
{
    get { return outputFile; }
    set
    {
        outputFile = value;
        OnPropertyChanged("OutputFile");
    }
}

我像这样在 MainWindow.XAML 中绑定(bind)

<cust:FileBrowserTextBox  Label="Input File" FilePath="{Binding InputFile}"/>
<cust:FileBrowserTextBox  Label="Output File" FilePath="{Binding OutputFile}"/>

运行它并得到这个错误

System.Windows.Data 错误:40:BindingExpression 路径错误:在“对象”“FileBrowserTextBox”(名称=“”)”上找不到“InputFile”属性。绑定(bind)表达式:路径=输入文件； DataItem='FileBrowserTextBox' (Name='');目标元素是“FileBrowserTextBox”(名称=“”)；目标属性是“FilePath”(类型“String”)System.Windows.Data 错误:40:BindingExpression 路径错误:在“对象”“FileBrowserTextBox”(名称=“”)”上找不到“OutputFile”属性。绑定(bind)表达式:路径=输出文件； DataItem='FileBrowserTextBox' (Name='');目标元素是“FileBrowserTextBox”(名称=“”)；目标属性是“FilePath”(类型“String”)

这基本上意味着 UserControl 中没有 InputFile 和 OutputFile，但我试图将控件的 FilePath 属性与模型的 InputFile 和 OutputFile 绑定(bind)，为什么不起作用？

提前致谢。

Answer 1

当你这样做的时候

DataContext="{Binding RelativeSource={RelativeSource Self}}"

在 FileBrowserTextBox 中，您覆盖了继承的 DataContext 更改绑定(bind)上下文。这意味着它将尝试在 FileBrowserTextBox 控件中查找 InputFile 和 OutputFile 属性。删除该行并更改 FileBrowserTextBox 中的绑定(bind)，这样它们就不会影响 DataContext，例如使用 RelativeSource ，类似于:

<TextBlock Grid.Column="0" Name="lblLabel" Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type UserControl}}, Path=Label}" MinWidth="150"/>
<TextBox Grid.Column="2" Name="txtFilepath" Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type UserControl}}, Path=FilePath}"/>

还在 PropertyChangedCallback 中为 Label 和 FilePath 你做:

fileBrowserTextBox.txtFilepath.Text = (string)e.NewValue;
fileBrowserTextBox.lblLabel.Text = (string)e.NewValue;

如果您只想更改 UI，则根本不需要处理属性更改回调。您已经在 XAML 中使用了绑定(bind)，它应该为您执行此操作，采用绑定(bind)上下文很好，上面的行只会用固定值覆盖这些绑定(bind)