Question

我正在创建一个UserControl对象，我正在尝试使用Binding（使用PropertyChanged）分配值。我创建了一个原型，当我在ViewModel中赋值时，该值不会出现或修改UserControl组件，但如果我直接在视图中的UserControl对象中赋值，则修改有效。我想了解我做错了什么，因为如果我只是在我的窗口上添加一个对象并直接绑定（再次使用PropertyChanged），我的工作正常。请遵循以下代码。

感谢您的帮助。

最诚挚的问候，

古斯塔沃。

用户控件：

<UserControl x:Class="WpfControlLibrary1.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" 
         mc:Ignorable="d" 
         d:DesignHeight="30" d:DesignWidth="300">
<Grid>
    <TextBlock Text="{Binding Title}" />
</Grid>
</UserControl>

用户控制的代码：

    public partial class UserControl1 : UserControl
{
    public UserControl1()
    {
        InitializeComponent();
    }

    #region Title Property

    public static String GetTitle(DependencyObject obj)
    {
        return (String)obj.GetValue(TitleProperty);
    }

    public static void SetTitle(DependencyObject obj, String value)
    {
        obj.SetValue(TitleProperty, value);
    }

    public static readonly DependencyProperty TitleProperty =
        DependencyProperty.RegisterAttached(
            "Title",
            typeof(String),
            typeof(UserControl1),
            new FrameworkPropertyMetadata(TitleChangedCallback)
            );

    private static void TitleChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        UserControl1 _this = (d as UserControl1);
    }

    private String title;
    public String Title
    {
        get { return title; }
        set
        {
            title = value;
            OnPropertyChanged("Title");
        }
    }

    #endregion

    #region INotifyPropertyChanged event and method

    public event PropertyChangedEventHandler PropertyChanged;

    // Create the OnPropertyChanged method to raise the event 
    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }

    #endregion

**我的窗口：**

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:uc="clr-namespace:WpfControlLibrary1;assembly=WpfControlLibrary1"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <uc:UserControl1 Title="{Binding TitleVM, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</Grid>
</Window>

**我的Code-Behind / ViewModel：**

public partial class MainWindow : INotifyPropertyChanged
{
    // Notify WPF that Counter changed
    public event PropertyChangedEventHandler PropertyChanged;

    public MainWindow()
    {
        InitializeComponent();

        TitleVM = "açsldkfjasçldkfj";
    }

    private String titleVM;
    public String TitleVM
    {
        get { return titleVM; }
        set
        {
            titleVM = value;
            OnPropertyChanged("TitleVM");
        }
    }

    // Create the OnPropertyChanged method to raise the event 
    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }

}

Answer 1

您的Window没有DataContext。绑定无法解决。

试试这个：

public MainWindow()
{
    InitializeComponent();

    DataContext = this; //This is what you're missing!

    TitleVM = "açsldkfjasçldkfj";
}

编辑：

你在UserControl

中也缺少同样的东西

public UserControl1()
{
    InitializeComponent();
    DataContext = this;
}

Answer 2

在HighCore的帮助下，我发现了一个问题，另一个问题是我的UserControl没有定义名称。

刚刚提出：

x:Name="UserControl"

进入UserControl的XAML并将工作。此外，我已将我的代码修改为：

        public String Title
    {
        get { return (String)base.GetValue(TitleProperty); }
        set { base.SetValue(TitleProperty, value); }
    }

    public static readonly DependencyProperty TitleProperty =
     DependencyProperty.RegisterAttached(
         "Title",
         typeof(String),
         typeof(UserControl1),
         new FrameworkPropertyMetadata(null)
         );

我们眼中的清洁代码。

PS：没有必要提出：

DataContext = this;

关于UserControl的代码。至少在这里只会导致bug，没有值出现。

感谢HighCore为您提供帮助。

对UserControl中的绑定感到困惑

2 个答案: