CODEWITHSUNDEEP
c#wpfxamlpropertychanged
SergS
SergS

Reputation: 39

Why ItemsControl does not refreshed

I have the following xaml:

<Window.DataContext>
    <local:CalendarViewModel />
</Window.DataContext>
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition
            Width="55*" />
        <ColumnDefinition
            Width="27*" />
    </Grid.ColumnDefinitions>
    <local:UserControlCalendar
        x:Name="ControlCalendar"
        Grid.Column="0">
    </local:UserControlCalendar>
    <ItemsControl
        x:Name="HistoryControl"
        Grid.Column="1"
        Width="210"
        Margin="30,10,0,0"
        HorizontalAlignment="Left"
        VerticalAlignment="Top"
        ItemTemplate="{StaticResource DataTemplate.HistoryItems}"
        ItemsPanel="{StaticResource ItemsPanel.Vertical}"
        ItemsSource="{Binding ListHistoryItems, Mode=OneWay}">
        <ItemsControl.ItemContainerStyle>
            <Style>
                <Setter Property="FrameworkElement.Margin" Value="0,10,0,0" />
            </Style>
        </ItemsControl.ItemContainerStyle>
    </ItemsControl>
</Grid>

When select a date in UserControlCalendar should change the contents of the "HistoryControl". In ViewModel Property ListHistoryItems changed, but ItemsControl in UserControl don't refreshed. This is ViewModel:

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
namespace CustomCalendar
{
  public class CalendarViewModel :  INotifyPropertyChanged
  {
    private ObservableCollection<HistoryItems> _listHistoryItems;
    private DateTime _selectedDate;

    public CalendarViewModel()
    {
    }

    public DateTime SelectedDate
    {
        get { return _selectedDate; }
        set
        {
            _selectedDate = value;
            if (_selectedDate != null)
            {
                ListHistoryItems = new ObservableCollection<HistoryItems>(GetHistoryItems(_selectedDate));
            }
        }
    }

    public ObservableCollection<HistoryItems> ListHistoryItems
    {
        get { return _listHistoryItems; }
        set
        {
            _listHistoryItems = value;
            RaisePropertyChanged("ListHistoryItems");
        }
    }

    protected virtual void RaisePropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    public event PropertyChangedEventHandler PropertyChanged;
  }
}

The problem is that Event PropertyChanged are always null. Why? Thanks in advance for your help.

Upvotes: 0

Views: 80

Answers (2)

SergS
SergS

Reputation: 39

I found my mistake. To transfer SelectedDate of the UserControlCalendar in the MainWindow, I have created in UserControlCalendar new ViewModel. Therefore, nothing worked. Now I removed that object, and all works fine. Now there's another question, how to transfer the SelectedDate in the ViewModel. I think the use of Prism and EventAggregator.

Upvotes: 0

Jon Koivula
Jon Koivula

Reputation: 947

ObservableCollection automatically notifyi UI if Collection changes. If the HistoryModel properties changes, yhen you need to call RaisePropertyChanged for that Property to notfyi UI. And if you make new ObservableCollection via new keyword, you need to refresh it to control.ItemsSource.

Also those controls that should show value of historymodel, use binding path=propertyname

Upvotes: 1

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