WPF自定义控件，DependencyProperty问题

本文关键字：问题 DependencyProperty 自定义控件 WPF | 更新日期: 2023-09-27 18:01:35

我有一个自定义控件的测试代码设置:

/// <summary>
    /// Interaction logic for UCTest.xaml
    /// </summary>
    public partial class UCTest : UserControl
    {
        public static readonly DependencyProperty LastNameProperty =
       DependencyProperty.Register("LastName", typeof(string), typeof(UCTest),
      new PropertyMetadata("No Name", LastNameChangedCallback, LastNameCoerceCallback),
      LastNameValidateCallback);
        private static void LastNameChangedCallback(
             DependencyObject obj, DependencyPropertyChangedEventArgs e)
        {
            Console.WriteLine(e.OldValue + " " + e.NewValue);
        }
        private static object LastNameCoerceCallback(DependencyObject obj, object o)
        {
            string s = o as string;
            if (s.Length > 8)
                s = s.Substring(0, 8);
            return s;
        }
        private static bool LastNameValidateCallback(object value)
        {
            return value != null;
        }

        public string LastName
        {
            get
            {
                return (string)GetValue(LastNameProperty);
            }
            set
            {
                SetValue(LastNameProperty, value);
            }
        }

        public UCTest()
        {
            InitializeComponent();
        }
    }

XAML代码中没有什么特别的:

<UserControl ...>
    <Grid DataContext="{Binding}">
    </Grid>
</UserControl>

View-Model中的代码:

public class ViewModel : DependencyObject
    {
        public static readonly DependencyProperty LastNameProperty =
              DependencyProperty.Register("LastName", typeof(string), typeof(ViewModel));
        public string LastName
        {
            get
            {
                return (string)GetValue(LastNameProperty);
            }
            set
            {
                SetValue(LastNameProperty, value);
            }
        }
     }

mainwindow . xml .cs中的代码:

public MainWindow()
        {
            InitializeComponent();
            var viewModel = new ViewModel();
            DataContext = viewModel;
            viewModel.LastName = "asdf";
            viewModel.LastName = "56udfh";
            viewModel.LastName = "09ualkja";
        }

主窗口。XAML代码:

<Window...>
    <Grid>
        <CustomControlTest:UCTest LastName="{Binding LastName}"/>
    </Grid>
</Window>

我设置了断点并设置为"When Hit"。输出(下面)显示，只有在最后一次执行"LastName"时才调用要更新的属性。我希望它在每次执行时都调用on更改…知道为什么吗?

Step into: Stepping over non-user code 'CustomControlTest.App.App'
Step into: Stepping over non-user code 'CustomControlTest.App.InitializeComponent'
Function: CustomControlTest.UCTest.LastNameValidateCallback(object), Thread: 0x1DDC Main Thread
Function: CustomControlTest.UCTest.LastNameValidateCallback(object), Thread: 0x1DDC Main Thread
Function: CustomControlTest.UCTest.LastNameValidateCallback(object), Thread: 0x1DDC Main Thread
Function: CustomControlTest.UCTest.LastNameCoerceCallback(System.Windows.DependencyObject, object), Thread: 0x1DDC Main Thread
Function: CustomControlTest.UCTest.LastNameValidateCallback(object), Thread: 0x1DDC Main Thread
Function: CustomControlTest.UCTest.LastNameValidateCallback(object), Thread: 0x1DDC Main Thread
Function: CustomControlTest.UCTest.LastNameCoerceCallback(System.Windows.DependencyObject, object), Thread: 0x1DDC Main Thread
Function: CustomControlTest.UCTest.LastNameChangedCallback(System.Windows.DependencyObject, System.Windows.DependencyPropertyChangedEventArgs), Thread: 0x1DDC Main Thread
No Name 09ualkja

谢谢,

PS，这是我上一篇文章的后续问题。我想我要开始一个新的，因为真正的问题与我原来的帖子无关。:)

WPF自定义控件，DependencyProperty问题

控件没有加载到MainWindow构造函数中，所以绑定还没有建立。您可以通过在最后一次赋值、更改处理程序和构造函数末尾设置断点来检查这一点。在UCTest的属性改变之前，你会看到构造函数完成了。

您可以通过使用Dispatcher延迟分配来解决这个问题:

this.Dispatcher.BeginInvoke((Action)(() =>
{
    viewModel.LastName = "asdf";
    viewModel.LastName = "56udfh";
    viewModel.LastName = "09ualkja";
}),
DispatcherPriority.DataBind);
相关文章：