Try to understand WPF. This is my test classes:
public partial class MainWindow : Window, INotifyPropertyChanged
{
private ObservableCollection<string> _myList = new ObservableCollection<string>();
public ObservableCollection<string> MyList
{
get { return _myList; }
set
{
_myList = value;
RaisePropertyChanged("_myList");
}
}
public MainWindow()
{
InitializeComponent();
comboBox1.DataContext = _myList;
}
private void button1_Click(object sender, RoutedEventArgs e)
{
MyList = AnotherClass.SomeMethod();
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
internal static class AnotherClass
{
public static ObservableCollection<string> SomeMethod()
{
return new ObservableCollection<string> {"this","is","test"};
}
}
And this is XAML
<Grid>
<ComboBox Height="23" HorizontalAlignment="Left" Margin="65,51,0,0" Name="comboBox1" VerticalAlignment="Top" Width="120" ItemsSource="{Binding}" />
<Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="310,51,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
</Grid>
How to make this code work? I want ComboBox data will be changed after I click on the button and MyList is updated. PropertyChangedEventHandler is always null.
The problem is that you are directly setting the original list onto the Window.DataContext
, so nothing ever listens to the windows' PropertyChanged
event.
To solve this, set the DataContext
to the window itself:
this.DataContext = this;
and then change the Binding
so refer to the property:
<ComboBox ItemsSource="{Binding MyList}" />
You will also need to change your property definition so that it raises the name of the property being changed, not the name of the member:
this.RaisePropertyChanged("MyList");
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