绑定到UserControl中的元素

如何解决绑定到UserControl中的元素

C＃，WPF。

我试图用元素绑定到对象层次结构中的属性的方法来实现UserControl。我一直在使用this作为参考。

我创建了以下最小示例。它实现了UserControl的三个实例，每个文本框代表一个文件名。依赖项属性用于允许绑定。尽管执行没有错误，但文本框为空白。它们应包含“ test1”，“ test2”和“ test3”。我想念什么？

主窗口：

<Window x:Class="CustomControlTest.MainWindow"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
          xmlns:mycontrols="clr-namespace:MyControls"
          mc:Ignorable="d"
          Title="MainWindow" Height="100" Width="800">
      <Grid>
          <StackPanel Orientation="Vertical" DataContext="{Binding ElementName=parent}">
              <mycontrols:DataFileControl x:Name="Ctrl1" FName="{Binding Path=project.File1.Filename}"/>
              <mycontrols:DataFileControl x:Name="Ctrl2" FName="{Binding Path=project.File2.Filename}"/>
              <mycontrols:DataFileControl x:Name="Ctrl3" FName="{Binding Path=project.File3.Filename}"/>
          </StackPanel>
      </Grid>
</Window>

namespace CustomControlTest
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Project project = new Project();
        public MainWindow()
        {
            InitializeComponent();
            project.File1.Filename = "test1";
            project.File2.Filename = "test2";
            project.File3.Filename = "test3";
        }
        
    }

    public class Project : INotifyPropertyChanged
    {
        public DataFile File1 { get; set; } = new DataFile();
        public DataFile File2 { get; set; } = new DataFile();
        public DataFile File3 { get; set; } = new DataFile();
    
        public event PropertyChangedEventHandler PropertyChanged;
    }

    public class DataFile : INotifyPropertyChanged
    {
        public string Filename { get; set; } = "";
    
        public event PropertyChangedEventHandler PropertyChanged;
    }  
}

UserControl：

<UserControl x:Class="MyControls.DataFileControl"
             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="40"
             d:DesignWidth="800"
             Name="TheCtrl">
    <Grid Height="20">
        <TextBox Name="filenameTextBox" Margin="5,5,0" Text="{Binding ElementName=TheCtrl,Path=FName,Mode=TwoWay}"/>
    </Grid>
</UserControl>

namespace MyControls
{
    public partial class DataFileControl : System.Windows.Controls.UserControl
    {

        public string FName
        {
            get { return (string)GetValue(FNameProperty); }
            set { SetValue(FNameProperty,value); }
        }

        public static readonly DependencyProperty FNameProperty =
            DependencyProperty.Register("FName",typeof(string),typeof(DataFileControl),new PropertyMetadata(null));


        public DataFileControl()
        {
            InitializeComponent();
        }

    }
}

解决方法

表达式

FName="{Binding Path=project.File1.Filename}"

需要在当前DataContext中尚未设置的名为project的公共属性。调试应用程序时，您应该已经在Visual Studio的“输出”窗口中注意到一条数据绑定错误消息。

更改为

public Project project { get; } = new Project();

public MainWindow()
{
    InitializeComponent();
    project.File1.Filename = "test1";
    project.File2.Filename = "test2";
    project.File3.Filename = "test3";
    DataContext = this;
}

---

或者，将Project实例用作DataContext（并因此使其成为视图模型）

private readonly Project project = new Project();

public MainWindow()
{
    InitializeComponent();
    project.File1.Filename = "test1";
    project.File2.Filename = "test2";
    project.File3.Filename = "test3";
    DataContext = project;
}

并将绑定表达式更改为

FName="{Binding File1.Filename}"