How to update ObservableCollection in UI?

Question

foreach (var t in ((App)App.Current).CollectionMessages)
  if (t.Uid.ToString() == uid)
    t.TexT = z;

The item in CollectionMessages, filed TexT changes Text to what I want. But the UI has no changes, it shows old value. What's wrong?Please help me.

Xaml:

   <Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <StackPanel Margin="0,0,0,0">
        <TextBlock Text="Диалоги" Style="{StaticResource PhoneTextNormalStyle}" FontSize="{StaticResource PhoneFontSizeLarge}"/>
    </StackPanel>
<Grid Grid.Row="2">
                <Grid d:LayoutOverrides="GridBox" >
                    <ListBox  x:Name="mess_list"  ItemsSource="{Binding}" >
                        <ListBox.ItemTemplate>
                            <DataTemplate >
                                <Grid>
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition Width="Auto"/>
                                        <ColumnDefinition Width="*"/>
                                    </Grid.ColumnDefinitions>

                                        <TextBlock Text="{Binding TexT}" " />

...

score 3 · Answer 1 · answered Sep 03 '11 at 18:57

3

You need to make sure that the class of which t is a type implements INotifyPropertyChanged (MSDN), and fires the PropertyChanged event when you set TexT.

answered Sep 03 '11 at 18:57

i_am_jorf

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ChrisF · Answer 2 · 2011-09-03T21:02:21.200

3

You need to implement the INotifyPropertyChanged interface and raise a property changed event so that the UI knows it has to update.

This How to: page has a worked example. You basically need this code:

public event PropertyChangedEventHandler PropertyChanged;

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

which gets called when the things you want to update get changed. So the code for TexT becomes:

private string localTexT
public string TexT
{
    get { return localTexT; }
    set
    {
        localTexT = value;
        NotifyPropertyChanged("TexT");
    }
}

From your update it looks like you've got the binding of the ItemsSource and TextBlock correct. However, have you set the DataContext of the view?

edited Sep 03 '11 at 21:02

answered Sep 03 '11 at 18:58

ChrisF

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NotifyPropertyChanged was fired but nothing in UI was changed. – SevenDays Sep 03 '11 at 19:18
@wsevendays - Would need to see the XAML. Are you using MVVM? – ChrisF Sep 03 '11 at 19:28
Not, I'm using ItemsSource property. – SevenDays Sep 03 '11 at 19:47
@wsevendays - edit the XAML into your question. It will help to see how the binding's defined. – ChrisF Sep 03 '11 at 19:48
Check my edit. And also CollectionMessages is ObservableCollection – SevenDays Sep 03 '11 at 20:58
hmm..I never set this, my code works without it before this time. full code : http://pastebin.com/gurMVfKi – SevenDays Sep 03 '11 at 21:43

How to update ObservableCollection in UI?

2 Answers2