Question

I’ve got a very strange issue while parsing an external XAML file. The pre-history is that I want to load an external XAML file with content to process. But I want to load as many different files as I want. That happens by unloading the old and loading the new one.

My issue is:
When I load a xaml the first time, everything is good, all as it should be.
But when I load the same xaml the second time, every entry of the object im Loading is there twice. If I run this again, every object is there three times and so on…

To debug the project yourself, download it here. The function starts at line 137 in the file “Control Panel.xaml.cs”. I realy don’t know what this is. Is it my fault or simply a bug? If yes, is there a workaround?

    /// <summary>
    /// Load a xaml file and parse it
    /// </summary>
    public void LoadPresentation()
    {
        this.Title = "Control Panel - " + System.IO.Path.GetFileName(global.file);

        System.IO.FileStream XAML_file = new System.IO.FileStream(global.file, System.IO.FileMode.Open);
        try
        {
            System.IO.StreamReader reader = new System.IO.StreamReader(XAML_file);
            string dump = reader.ReadToEnd(); //This is only for debugging purposes because of the strange issue...
            XAML_file.Seek(0, System.IO.SeekOrigin.Begin);

            presentation = (ResourceDictionary)XamlReader.Load(XAML_file);

            //Keys the resourceDictionary must have to be valid
            if (presentation["INDEX"] == null || presentation["MAIN_GRID"] == null || presentation["CONTAINER"] == null || presentation["LAYOUTLIST"] == null)
            {
                throw new Exception();
            }

            //When this list is loaded, every item in it is there twice or three times or four... Why????
            TopicList Index = null;
            Index = (TopicList)presentation["INDEX"];

            for (int i = 0; i < topics.Count; )
            {
                topics.RemoveAt(i);
            }

            foreach (TopicListItem item in Index.Topics)
            {
                topics.Insert(item.TopicIndex, (Topic)presentation[item.ResourceKey]);
            }

            lv_topics.SelectedIndex = 0;
            selectedIndex = 0;
        }
        catch
        {
            System.Windows.Forms.MessageBox.Show("Failed to load XAML file \"" + global.file + "\"", "Parsing Error", System.Windows.Forms.MessageBoxButtons.OK, System.Windows.Forms.MessageBoxIcon.Error);
            presentation = null;
        }
        finally
        {
            XAML_file.Close();
        }
    }

Edit:

I have tried to serialize the object that was read from the XamlReader and in the output was nowhere any childelement… But if I pull the object out of the dictionary, the children are all there (duplicated and triplicated, but there).

I have already tried to clear the list over

topics.Clear();

and

topics=new ObservableCollection<TopicListItem>();
lv_topics.ItemsSource=topics;

Answer 1

Try Index.Topics.Clear() after loading the Topics into your topics object. That appears to get rid of the duplication.

//When this list is loaded, every item in it is there twice or three times or four... Why???? 
TopicList Index = null; 
Index = (TopicList)presentation["INDEX"]; 

topics.Clear();

foreach (TopicListItem item in Index.Topics) 
{ 
    topics.Insert(item.TopicIndex, (Topic)presentation[item.ResourceKey]); 
} 

Index.Topics.Clear();        //Adding this will prevent the duplication
lv_topics.SelectedIndex = 0; 
selectedIndex = 0;