WPF 自定义控件的依赖属性无意中影响了其他控件答案

【问题标题】：WPF Custom Control's Dependency Property unintentionally affecting other controlsWPF 自定义控件的依赖属性无意中影响了其他控件
【发布时间】：2016-05-06 10:32:41
【问题描述】：

我正在制作一个应该记录鼠标位置的窗口。我创建了一个用户控件，它应该显示该位置标签的当前坐标并允许用户更改它们。

它很好用，除了当一个更新时它们都会改变。

我认为这与依赖属性是静态注册的事实有关。它们需要是依赖属性，因为我需要能够将它们从 xaml 绑定到我的模型。

如何让用户控件相互独立？

<UserControl x:Class="SapFormFiller.SerializableMouseEditorControl"
         ...
         DataContext="{Binding RelativeSource={RelativeSource Self}}">
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="60*"/>
        ...
        <ColumnDefinition Width="20*"/>            
    </Grid.ColumnDefinitions>
    <Label Content="{Binding LabelText}"></Label>
    <Label Grid.Column="1" Content="{Binding SerializableMouseKeyboardEventArgs.X}"/>
    <Label Grid.Column="2" Content="{Binding SerializableMouseKeyboardEventArgs.Y}"/>
    <Button Grid.Column="3" Margin="0,0,0.4,0" Click="ButtonBase_OnClick">Edit</Button>
</Grid>

cs:

public partial class SerializableMouseEditorControl : UserControl
{
    public static DependencyProperty LabelTextProperty = DependencyProperty.Register(
        "LabelText", typeof (string), typeof (SerializableMouseEditorControl), new PropertyMetadata(default(string)));

    public string LabelText
    {
        get { return (string) GetValue(LabelTextProperty); }
        set { SetValue(LabelTextProperty, value); }
    }
    public static DependencyProperty SerializableMouseKeyboardEventArgsProperty = DependencyProperty.Register(
        "SerializableMouseKeyboardEventArgs", typeof (SerializableMouseKeyboardEventArgs), typeof (SerializableMouseEditorControl), new PropertyMetadata(new SerializableMouseKeyboardEventArgs()));

    public SerializableMouseKeyboardEventArgs SerializableMouseKeyboardEventArgs
    {
        get { return (SerializableMouseKeyboardEventArgs) GetValue(SerializableMouseKeyboardEventArgsProperty); }
        set { SetValue(SerializableMouseKeyboardEventArgsProperty, value); }
    }
    public SerializableMouseEditorControl()
    {
        InitializeComponent();
        SerializableMouseKeyboardEventArgs = new SerializableMouseKeyboardEventArgs();
    }

    private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
    {
        SerializableMouseKeyboardEventArgs.Update();
    }
}

SerializableMouseKeyboardEventArgs：

public class SerializableMouseKeyboardEventArgs : INotifyPropertyChanged
{
    public int X
    {
        get { return _x; }
        set
        {
            _x = value; 
            OnPropertyChanged("X");
        }
    }

    public int Y
    {
        get { return _y; }
        set
        {
            _y = value;
            OnPropertyChanged("Y");

        }
    }
    ...
    IKeyboardMouseEvents gkme;        
    private int _x = 0;
    private int _y=0;

    public override string ToString(){...}
    public SerializableMouseKeyboardEventArgs()
    {
        gkme = Hook.GlobalEvents();
    }
    public void Update()
    {
        IsEditing = true;
        gkme.MouseClick += Gkme_MouseClick;
    }

    private void Gkme_MouseClick(object sender, MouseEventArgs e)
    {
        if(e.Button==MouseButtons.Left)
        {
            this.X = e.X;
            this.Y = e.Y;
        }
        else if (e.Button == MouseButtons.Right)
        {
            gkme.MouseClick -= Gkme_MouseClick;
            IsEditing = false;
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

【问题讨论】：

您是否在gkme.MouseClick -= Gkme_MouseClick; 设置了断点以确保处理程序实际上已分离？
问题很可能是您将new SerializableMouseKeyboardEventArgs() 创建为默认值。这使它在所有人之间共享。添加一个非静态 ctor 并从那里设置属性。
如果我将其设置为default()，那么所有依赖属性都是null，并且在单击编辑按钮时会出现空引用异常。是的，处理程序成功分离。

标签： c# wpf data-binding user-controls dependency-properties

【解决方案1】：

这一行

new PropertyMetadata(new SerializableMouseKeyboardEventArgs()));

看起来它可能会给您带来问题。我的情况是使用 new 关键字声明默认值导致 UserControl 的一个实例与另一个实例共享该属性值。

尝试在构造函数中初始化任何此类属性，它可能会起作用。

【讨论】：