wpf - 可观察集合未在 UI 更改时更新

Question

我正在尝试将可观察集合绑定(bind)到用户控件，但它不会根据用户更改进行更新，但会在通过代码更改用户控件时进行更新。以下是我试过的一个例子。它可能有点长，但它正在运行，因此您可以按原样复制和粘贴代码。

请在帖子末尾查看我的问题。

--Customer.cs

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.ComponentModel;namespace TestMVVM{    class Customer : INotifyPropertyChanged    {        private string firstName;        private string lastName;        public string FirstName        {            get { return firstName; }            set            {                if (firstName != value)                {                    firstName = value;                    RaisePropertyChanged("FirstName");                }            }        }        public string LastName        {            get { return lastName; }            set            {                if (lastName != value)                {                    lastName = value;                    RaisePropertyChanged("LastName");                }            }        }        #region PropertChanged Block        public event PropertyChangedEventHandler PropertyChanged;        private void RaisePropertyChanged(string property)        {            if (PropertyChanged != null)            {                PropertyChanged(this, new PropertyChangedEventArgs(property));            }        }        #endregion    }}

--UCTextBox.xaml

<UserControl x:Class="TestMVVM.UCTextBox"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Height="40" Width="200">
<Grid>
    <TextBox Height="23" HorizontalAlignment="Left" Margin="10,10,0,0" Name="txtTextControl" 
             VerticalAlignment="Top" Width="120" />
</Grid>

--UCTextBox.xaml.cs

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes;using System.Collections.ObjectModel;using System.ComponentModel;namespace TestMVVM{    ///     /// Interaction logic for UCTextBox.xaml    ///     public partial class UCTextBox : UserControl, INotifyPropertyChanged    {        public UCTextBox()        {            InitializeComponent();        }        public static readonly DependencyProperty TextProperty =        DependencyProperty.Register("Text", typeof(string), typeof(UCTextBox),        new UIPropertyMetadata(string.Empty, new PropertyChangedCallback(textChangedCallBack)));        static void textChangedCallBack(DependencyObject property, DependencyPropertyChangedEventArgs args)        {            UCTextBox pasTextBox = (UCTextBox)property;            pasTextBox.txtTextControl.Text = (string)args.NewValue;        }        public string Text        {            get            {                return (string)GetValue(TextProperty);            }            set            {                SetValue(TextProperty, value);                NotifyPropertyChanged("Text");            }        }        private void NotifyPropertyChanged(String info)        {            if (PropertyChanged != null)            {                PropertyChanged(this, new PropertyChangedEventArgs(info));            }        }        #region INotifyPropertyChanged Members        public event PropertyChangedEventHandler PropertyChanged;        #endregion    }}

-- Window1.xaml

<Window x:Class="TestMVVM.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:TestMVVM"
Title="Window1" Height="300" Width="300">
<Grid>
    <local:UCTextBox x:Name="txtUC" />
    <Button Height="23" HorizontalAlignment="Left" Margin="39,0,0,82" 
            Name="btnUpdate" VerticalAlignment="Bottom" Width="75" Click="btnUpdate_Click">Update</Button>
    <Button Height="23" Margin="120,0,83,82" Name="btnChange" VerticalAlignment="Bottom" Click="btnChange_Click">Change</Button>
</Grid>

-- Window1.xaml.cs

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes;using System.Collections.ObjectModel;namespace TestMVVM{    ///     /// Interaction logic for Window1.xaml    ///     public partial class Window1 : Window    {        CustomerHeaderViewModel customerHeaderViewModel = null;        public Window1()        {            InitializeComponent();            customerHeaderViewModel = new CustomerHeaderViewModel();            customerHeaderViewModel.LoadCustomers();            txtUC.DataContext = customerHeaderViewModel.Customers[0];            Binding binding = new Binding();            binding.Source = customerHeaderViewModel.Customers[0];            binding.Path = new System.Windows.PropertyPath("FirstName");            binding.Mode = BindingMode.TwoWay;            binding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;            txtUC.SetBinding(UCTextBox.TextProperty, binding);        }        private void btnUpdate_Click(object sender, RoutedEventArgs e)        {            MessageBox.Show(customerHeaderViewModel.Customers[0].FirstName);        }        private void btnChange_Click(object sender, RoutedEventArgs e)        {            txtUC.Text = "Tom";        }    }    class CustomerHeaderViewModel    {        public ObservableCollection Customers { get; set; }        public void LoadCustomers()        {            ObservableCollection customers = new ObservableCollection();            customers.Add(new Customer { FirstName = "Jim", LastName = "Smith", NumberOfContracts = 23 });            Customers = customers;        }    }}

当我运行 Window1.xaml 时，我的用户控件将数据显示为“Jim”。现在，当我将文本更改为“John”并单击“更新”时，消息框仍然显示“Jim”，这意味着可观察集合没有得到更新。当我单击“更改”按钮时，用户控件将数据更改为“Tom”。现在，当我单击“更新”按钮时，消息框显示“Tom”。谁能告诉我如何通过更改用户控件中的数据而不是通过代码来实现可观察集合的更新？

Answer 1

那是因为您没有处理 txtTextControl.TextChanged 事件，所以您的 Text 依赖属性永远不会更新。

无论如何，您不需要使用 DependencyPropertyChangedCallback 和事件处理程序手动处理，您只需将 txtTextControl.Text 绑定(bind)到 Text 依赖属性:

<TextBox Height="23" HorizontalAlignment="Left" Margin="10,10,0,0" Name="txtTextControl" 
         VerticalAlignment="Top" Width="120"
         Text="{Binding Path=Text, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type local:UCTextBox}}}"/>