c# - 在 WPF 中使用 INotifyPropertyChanged

Question

您好，我正在尝试使用 NotifyPropertyChanged 来更新我绑定(bind)属性的所有位置。对于我搜索过的内容，INotifyPropertyChanged 是针对这种情况指示的。

所以我需要帮助，因为我不明白我在这里有什么问题。我真的不知道如何处理 PropertyChange 事件。我的问题是，他什么时候改变？我还需要他做什么？

数据网格:

<ListView Name="listView" ItemsSource="{Binding Categories}"/>

我更改类别属性时的示例:

DataTest dtTest = new DataTest();

public MainWindow()
{
    InitializeComponent();
    this.DataContext = dtTest;
}

private void Button1_Click(object sender, RoutedEventArgs e)
{
    //Here i pick up a string from a textBox, where i will insert in a Table of my DB,
    //Then i will do a query to my Table, and i will get a DataTable for example
    //Then i just put the contents into the DataView, so the value have changed.
    dtTest.Categories = dtTable.DefaultView;
    dtTest = dtTable.defaultView; (this only an example, i don't this for real.)
    //What i have to do now, to wherever i am binding (DataGrid, ListView, ComboBox)
    //the property to the new values automatically being showed in all places?
}

我的类(class):

public class DataTest : INotifyPropertyChanged
{
    private DataView categories;

    public event PropertyChangedEventHandler PropertyChanged; //What i have to do with this?

    private void NotifyPropertyChanged(string str)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(str));
        }
    }

    public DataView Categories
    {
        get { return categories; }
        set 
        {
            if (value != categories)
            {
                categorias = value;
                NotifyPropertyChanged("Categories");
            }
        }
    }
}

我的类(class)有 INotifyCollectionChanged:

public class DataTest : INotifyCollectionChanged
{
    public event NotifyCollectionChangedEventHandler CollectionChanged;

    private void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        if (CollectionChanged != null)
        {
            CollectionChanged(this, e);
        }
    }

    public DataView Categories
    {
        get { return categories; }
        set 
        {
            if (value != categories)
            {
                categories = value;
                OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, Categories));
            }
        }
    }
}

但为什么 PropertyChanged 总是 NULL？？？我必须做更多的事情，但我不知道该做什么。

提前致谢!

Answer 1

DataTest 类需要是绑定(bind)的 DataContext。您可以在代码隐藏中设置它(或无数其他方式，但为简单起见 - 只需在代码隐藏中进行)

public MainWindow() // constructor
{
    this.DataContext = new DataTest();
}

然后，使用绑定(bind)集的“源”，您可以指定“路径”，因此您的 xaml 如下所示:

<ListBox ItemsSource="{Binding Categories}" />

现在，如果属性“Categories”在代码中发生更改，您编写的 NotifyPropertyChanged 代码将提醒 Binding，Binding 反过来将访问该属性的公共(public) getter 并刷新 View 。