DataGrid does not updating with ObservableCollection

1
votes

I'm trying to learn MVVM (Using MVVMLight Toolkit). But i'm stuck.

In ViewModel have an ObservableCollection 

private ObservableCollection<Phone> _phoneNumbers;

public ObservableCollection<Phone> PhoneNumbers
{
    get { return _phoneNumbers; }
    private set
    {
        _phoneNumbers = value;
    }
}

In ViewModel constructor fill it in such way PhoneNumbers = new ObservableCollection<Phone>(Guest.Person.Phones);

In view have

<DataGrid x:Name="PhoneNumbersDataGrid" HorizontalAlignment="Left" Grid.Column="3" Grid.Row="11" VerticalAlignment="Top" Height="86" Width="auto" ItemsSource="{Binding PhoneNumbers, Mode=OneWay}" AutoGenerateColumns="False" IsReadOnly="True">
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding PhoneNumber}" Header="Phone Number" IsReadOnly="True"/>
        <DataGridTemplateColumn Header="Delete">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <Button Command="{Binding Guest.DeletePhoneCommand, Mode=OneWay, Source={StaticResource Locator}}">Delete</Button>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>

In DeletePhoneCommand I'm trying to change PhoneNumbers e.g. 

PhoneNumbers = new ObservableCollection<Phone>();
RaisePropertyChanged("PhoneNumbers");

Collection became empty but datagrid displays filled collection without any changes. "get" of Collection fires only when view is loading. Even when i RaisePropertyChanged("PhoneNumbers") it doesn't fire.

What am I doing wrong?

3
c#wpfmvvmdatagridobservablecollection

3 Answers

1
votes

If you want to notify the changes to your collection you should use Mode = TwoWay

Two way will enable any change in object is reflected to the UI and any change in UI is reflected in the object.

<DataGrid x:Name="PhoneNumbersDataGrid" HorizontalAlignment="Left" Grid.Column="3" Grid.Row="11" VerticalAlignment="Top" Height="86" Width="auto" ItemsSource="{Binding PhoneNumbers, Mode=TwoWay}" AutoGenerateColumns="False" IsReadOnly="True">
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding PhoneNumber,Mode=TwoWay}" Header="Phone Number" IsReadOnly="True"/>
                <DataGridTemplateColumn Header="Delete">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Command="{Binding Guest.DeletePhoneCommand, Mode=OneWay, Source={StaticResource Locator}}">Delete</Button>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
        </DataGrid>
0
votes

If I'm not mistaken, the binding is broken when you reinitialize the collection. to fix this you will have to work on the already initialized collection. e.g :

clear the list using the

PhoneNumbers.Clear()

to add to the list, using

PhoneNumbers.Add(item)

you don't need to raise the property changed event to update the list in the UI when you're using ObservableCollection. You will need it if you change a property of the item on the list.

0
votes

at first clear the list with 

Clear()

then add item

PhoneNumbers.Add(item)