INotifyPropertyChanged not working with traditonal binding but works with compiled binding

问题

I don't if I am doing something wrong or if there is something I am missing but the INotifyPropertyChanged works when I do it with compile time binding and doesn't work when I do it with traditional binding.

public class Students : INotifyPropertyChanged
{

    private string name;
    private string surname;


    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public string Name
    {
        get { return name; }
        set
        {
            if(value != name)
            {
                name = value;
                NotifyPropertyChanged();
            }

        }
    }

    public string Surname
    {
        get { return surname; }
        set
        {
            if (value != surname)
            {
                surname = value;
                NotifyPropertyChanged();
            }

        }
    }

    public Students()
    {
        Name = "John";
        Surname = "Smith";
    }


}

MainPage.xaml

<Page.DataContext>
    <local:Students/>
</Page.DataContext>

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <StackPanel Margin="0,200,0,0">
        <TextBlock Text="{Binding Name}"/>
        <TextBlock Text="{Binding Surname}"/>
        <Button Content="Change Name" Click="change_name"/>
        <Button Content="Change Surname" Click="change_surname"/>
    </StackPanel>

</Grid>

MianPage.xaml.cs

public sealed partial class MainPage : Page
{
    Students st;
    public MainPage()
    {
        this.InitializeComponent();
        st = new Students();
    }

    private void change_name(object sender, RoutedEventArgs e)
    {
        st.Name = "MM";
    }

    private void change_surname(object sender, RoutedEventArgs e)
    {
        st.Surname = "SS";
    }
}

I am really confused, because when you bind with compile time binding, it works fine. What's going on?

回答1:

I don't see any place in which you are setting the current DataContext to your object.

 public MainPage()
    {
        this.InitializeComponent();
        st = new Students();
        this.DataContext = st;
    }

OR: You are setting a datacontext in your XAML, but you aren't referencing it.

<Page.DataContext>
<local:Students/>
</Page.DataContext>

You would need to reference that object from code if you intend to use it.

 private void change_name(object sender, RoutedEventArgs e)
    {
        ((Students)this.DataContext).Name = "MM";
    }

回答2:

I had a situation very similar to the author (if not the same) and only thing I did to fix it is I made my view model a public property. In case of the example above, it would be Students st; changed to public Students st {get; set;}

来源：https://stackoverflow.com/questions/33376304/inotifypropertychanged-not-working-with-traditonal-binding-but-works-with-compil

标签

xaml

data-binding

inotifypropertychanged

uwp