mvvmsilverlightwindows-phone

Getting MVVM ViewModel to bind to the View


I have the following code (changed object names, so syntax/spelling errors ignore).

public class ViewModel
{
    ViewModelSource m_vSource;

    public ViewModel(IViewModelSource source)
    {
        m_vSource= source;
        m_vSource.ItemArrived += new Action<Item>(m_vSource_ItemArrived);
    }

    void m_vSource_ItemArrived(Item obj)
    {
        Title = obj.Title;
        Subitems = obj.items;
        Description = obj.Description;
    }

    public void GetFeed(string serviceUrl)
    {
        m_vFeedSource.GetFeed(serviceUrl);
    }

    public string Title { get; set; }
    public IEnumerable<Subitems> Subitems { get; set; }
    public string Description { get; set; }
 }

Here is the code I have in my page's codebehind.

ViewModel m_vViewModel;

public MainPage()
{
    InitializeComponent();

    m_vViewModel = new ViewModel(new ViewModelSource());
    this.Loaded += new RoutedEventHandler(MainPage_Loaded);

    this.DataContext = m_vViewModel;
}

void MainPage_Loaded(object sender, RoutedEventArgs e)
{
    m_vViewModel.GetItems("http://www.myserviceurl.com");
}

Finally, here is a sample of what my xaml looks like.

<!--TitleGrid is the name of the application and page title-->
<Grid x:Name="TitleGrid" Grid.Row="0">
    <TextBlock Text="My Super Title" x:Name="textBlockPageTitle" Style="{StaticResource PhoneTextPageTitle1Style}"/>
    <TextBlock Text="{Binding Path=Title}" x:Name="textBlockListTitle" Style="{StaticResource PhoneTextPageTitle2Style}"/>
</Grid>

Is there anything I'm doing wrong here?


Solution

  • I think your ViewModel should implement the INotifyPropertyChanged interface:

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

    Then your property would look like that:

        private title;
        public string Title 
        { 
            get
            {
                return this.title;
            }
    
            set
            {
                if (this.title!= value)
                {
                    this.title= value;
                    this.RaisePropertyChanged("Title");
                }
            }
        }
    

    Michael