Items Not Displaying in GanttView

[Robert Kaucher]

I have created the following GanttView in my XAML

<telerik:RadGanttView HorizontalAlignment="Left"
                             Name="radGanttView1"
                             VerticalAlignment="Top"
                             Width="950" Height="450"
                             TasksSource="{Binding ItProjects}"
                             telerik:StyleManager.Theme="Metro">
           <telerik:RadGanttView.Columns>
               <telerik:ColumnDefinition MemberBinding="{Binding Duration}" Header="Duration" ColumnWidth="100" />
               <telerik:ColumnDefinition MemberBinding="{Binding Start}" Header="Start" ColumnWidth="55" />
               <telerik:ColumnDefinition MemberBinding="{Binding End}" Header="End" ColumnWidth="55"/>
           </telerik:RadGanttView.Columns>

       </telerik:RadGanttView>

And I have the following code behind...

private ClientContext _ctx;
private IEnumerable<ListItem> _items;
private string _listName = "IT Projects";
private List<GanttTask> _itProjects;
public List<GanttTask> ItProjects
{
    get
    {
        if (_itProjects == null)
        {
            _itProjects = new List<GanttTask>();
        }
        return _itProjects;
    }
    set
    {
        if (_itProjects != value)
        {
            _itProjects = value;
            NotifyPropertyChanged("ItProjects");
        }
    }
}



public MainPage()
{
    InitializeComponent();
    _itProjects = new List<GanttTask>();
    GetItProjects();
    this.DataContext = this;
}

private void GetItProjects()
{
    _ctx = ClientContext.Current;

    CamlQuery camlQry = new CamlQuery()
    {
        ViewXml = "<View><Query><Where><Neq><FieldRef Name=\"Status\" /><Value Type=\"Choice\">Completed</Value></Neq></Where><OrderBy><FieldRef Name=\"Title\" Ascending=\"True\" /></OrderBy></Query></View>"
    };
    ListItemCollection listItems = _ctx.Web.Lists.GetByTitle(_listName).GetItems(camlQry);

    _items = _ctx.LoadQuery(listItems.Include(
            item => item["Title"],
            item => item.Id,
            item => item["StartDate"],
            item => item["DueDate"]
        ));

    _ctx.ExecuteQueryAsync(onQuerySucceeded, onQueryFailed);
}

private void onQuerySucceeded(object sender, ClientRequestSucceededEventArgs args)
{

    Dispatcher.BeginInvoke(() => {
        foreach (ListItem item in _items)
        {
            try
            {
                ItProjects.Add(ConvertListItemToProject(item));
            }
            catch (Exception ex)
            {
                MessageBox.Show("Exception: " + ex.Message + "Stack: "+ ex.StackTrace);
            }
        }
        NotifyPropertyChanged("ItProjects");
    });
}

private void onQueryFailed(object sender, ClientRequestFailedEventArgs args)
{
    //TODO: Set an error state.
    MessageBox.Show(args.ErrorDetails.ToString());
}

private GanttTask ConvertListItemToProject(ListItem item)
{
    TimeSpan ts = DateTime.Parse(item["StartDate"].ToString()) - DateTime.Parse(item["DueDate"].ToString());

    return new GanttTask(DateTime.Parse(item["StartDate"].ToString()), DateTime.Parse(item["DueDate"].ToString()), item["Title"].ToString());
}

I end up with 16 items in my collection but I see nothing in the control. Any suggestions? I've been experimenting with NotifyPropertyChanged in different places. I am not certain what the issue may be, though.

[Miroslav Nedyalkov]

Hello Robert,

The problem in your code is that you create an empty list of items which doesn't rise change notifications (List<GanttTask>) and when your query finishes you don't replace the object and just rise the notification. As in your XAML you are binding the TasksSource dependency property to the view-model, it performs addition check and if the value haven't changed, no property changed notification is thrown inside the control and it doesn't update.

What I would suggest you is to either create a new list for the result or to use ObservableCollection instead of a simple List (this first one is preferable as it will perform better).

Hope this helps.

Kind regards,
Miroslav Nedyalkov
the Telerik team

[Robert Kaucher]

I used observable collection initially and I received this error.

http://www.telerik.com/community/forums/silverlight/ganttview/keynotfound.aspx 

[Miroslav Nedyalkov]

Hi Robert,

This was a bug which will be fixed in the 2012 Q2 release. In this case you could just change the way you work-around the issue using a new list just before throwing the notification.

Hope this helps.

All the best,
Miroslav Nedyalkov
the Telerik team

[Robert Kaucher]

Done! I was hoping that might have been fixed in an internal build but this is a really small project, so you suggestion is fine. Thanks!