Question

I build up a Office 2010 Word Add In, added a Windows Forms Element to it and there in an ElementHost object containing my WPF.

That’s the problem:
I got the problem, that common properties (DP’s) defined in the Xaml code and set in the ViewModel implementation (see code below) are not updated, even if I can’t find any wrong code while debugging. This applies only to the properties I got, furthermore i got some
ObservableCollection<> List’s which are updated without any problems. Got anybody an idea? I red that I may define the properties by myself within the Code using something like this:

public static readonly DependencyProperty DataSourceProperty = DependencyProperty.Register("DataSource",typeof(string),typeof(usercontrol1));

But this does not work too (I just added this line for example into the code-behind file of the Xaml file – and left anything else at it is)

My code looks this way:

Constructor of the Forms Element (it’s actually private because I implemented it as Singleton):

private Sidebar()
{
    InitializeComponent();
    this.DoubleBuffered = true;

    _wpfHost = new ElementHost();
    _wpfHost.Dock = DockStyle.Fill;

    _wpfUserControl = new WPFUI();

    _wpfHost.Child = _wpfUserControl;

    this.Controls.Add(_wpfHost);
}

Furthermore I created an underlying ViewModel and set this as DataContext Property of the WPFUI like this (it’s also a Singleton implementation because I wanted to access in a further implementation the same instance from several places, but this does not come into the game at this time):

public WPFUI()
{
    InitializeComponent();

    this.DataContext = myViewModel.GetInstance();
}

My ViewModel properties are defined and used this way:

public ObservableCollection<myListViewItem> PeopleEntityResultObjects { get; private set; }

private string _NumberOfPeople;
public string NumberOfPeople
{
    get { return _NumberOfPeople; }
    set { SetField(ref _NumberOfPeople, value, () => NumberOfPeople); }
}

And finally the Xaml looks like this:

<TabControl>
    <TabItem>
        <TabItem.Header>
            <StackPanel Orientation="Horizontal">
                <TextBlock Text=" People "/>
                <TextBlock Text="{Binding Path=NumberOfPeople}"/>
            </StackPanel>
        </TabItem.Header>

        <ScrollViewer x:Name="PeopleListScrollViewer">
            <ListView Name="PeopleListView" ItemsSource="{Binding Path=PeopleEntityResultObjects, Mode=OneWay}" IsSynchronizedWithCurrentItem="True">
            .
            .
            .
            </ListView>
        </ScrollViewer>
    </TabItem>
</TabControl>

Why is my ObservableCollection<> List updating but not the bound properties like

<TextBlock Text="{Binding Path=NumberOfPeople}"/>

? Can anybody guess, or i’m missing some basic property definition? (in a wpf application it is working that way).

EDIT

SetField() implementation:

protected virtual void OnPropertyChanged<T>(Expression<Func<T>> selectorExpression)
{
    if (selectorExpression == null)
        throw new ArgumentNullException("selectorExpression");

    MemberExpression body = selectorExpression.Body as MemberExpression;

    if (body == null)
        throw new ArgumentException("The body must be a member expression");

    OnPropertyChanged(body.Member.Name);
}

protected virtual void OnPropertyChanged(string propertyName)
{
    PropertyChangedEventHandler handler = PropertyChanged;

    if (handler != null) 
        handler(this, new PropertyChangedEventArgs(propertyName));
}

protected bool SetField<T>(ref T field, T value, Expression<Func<T>> selectorExpression)
{
    if (EqualityComparer<T>.Default.Equals(field, value)) return false;

    field = value;

    OnPropertyChanged(selectorExpression);

    return true;
}       

Regards,
Thomas

Answer 1

using the dispatcher object, already used to insert item’s into the UI bound list, is the key to accomplish this task successfully:

if (DispatcherObject.Thread != Thread.CurrentThread)
    DispatcherObject.Invoke(new Action(() => SetField(ref _numberOfPeople, value, () => NumberOfPeople)));
else
    SetField(ref _numberOfPeople, value, () => NumberOfPeople);