Question

我正在尝试了解WPF中的数据绑定。我有一个测试应用程序（如下）。我试图让数据更新进出XAML。即....

当我在XAML TextBox中编辑值时，我想要在中的c＃对象代码隐藏更新。
如果c＃发生变化（按下按钮模拟），我想要更新XAML TextBox。
我希望XAML列表框中的项目能够针对上述任一更改进行更新。

到目前为止，我已经获得No.1工作，但无法弄清楚如何让其他2人工作。

... MainWindow.xaml

<Window x:Class="MySimpleProgram.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="725"
        >
    <StackPanel Name="StackPanel1" Orientation="Horizontal">

        <TextBox Name="TextBox2" Text="{Binding Path=FirstName, Mode=TwoWay}" Height="23"/>

        <Button Name="Button1" Content="Change C# obj people[0]" Width="175" Height="20" Click="Button1_Click" />

        <ListBox Name="listPeople" DisplayMemberPath="FirstName"/>

    </StackPanel>
</Window>

... MainWindow.xaml.cs

namespace MySimpleProgram
{

    public class Person
    {
        public string FirstName { get; set; }
        public int Age { get; set; }
    }


    public partial class MainWindow : Window
    {
        public ObservableCollection<Person> people;

        public MainWindow()
        {
            InitializeComponent();

            people = new ObservableCollection<Person>(){ 
                new Person{ FirstName = "Shirley", Age = 22}, 
                new Person{ FirstName = "Roy", Age = 29},  
                new Person{ FirstName = "Manuel", Age = 34} };

            StackPanel1.DataContext = people[0];

            listPeople.ItemsSource = people;
        }


        private void Button1_Click(object sender, RoutedEventArgs e)
        {
            people[0].FirstName += "y";
        }

    }
}

4）另外如果我按下button1，listBox会更新textBox而不是+="y"部分提供的值 - 导致这种情况发生的原因是什么？

Answer 1

作为Sajeetharan said，您需要实施INotifyPropertyChanged，但要查看您的other question您实施的“不正确”。它不是“错误的”，因为它仍然可以工作，但它不是几乎所有人都使用的模式，如果你使用它们，可能会让其他开发者更难。

public class Person : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;    

    private String _firstName;
    private String _age;

    public string FirstName
    {
        get { return _firstName; }
        set
        {
            //If the value did not change we shouldn't trigger the event.
            if(Object.Equals(_firstName, value))
                return;

            _firstName = value;

            //Use a reuseable function to "raise" your event so it makes 
            // multiple properties easier. The standard name for this raising
            // function is OnXxxxxxx where Xxxxxxx is your Event name and should
            // be private or protected.
            OnPropertyChanged("FirstName")
        }
    }

    private OnPropertyChanged(string propertyName)
    {
        //Storing the event in a local temporary variable prevents
        // a potential NullRefrenceException when you are working
        // in a multitreaded enviorment where the last subscriber
        // could unsubscribe between the null check and the invocation.
        var tmp = PropertyChanged;
        if (tmp != null)
            tmp(this, new PropertyChangedEventArgs(propertyName));
    }

    public int Age 
    { 
        get {return _age;} 
        set
        {
            if(Object.Equals(_age, value))
                return;

            _age= value;
            OnPropertyChanged("Age")
        }
    }
}

Answer 2

如果您希望在应用程序中进行双向绑定，那么您的数据对象Person必须实现INotifyPropertyChanged

C＃和XAML之间的双向数据绑定更新

2 个答案: