Question

I am having trouble with declaratively setting the ItemsSource of a ListBox contained within a PivotItem in a simple Windows Phone 7 page. I can successfully set the ItemsSource in code behind.

Here is a snippet of the class that contains the ObservableCollection that I want to bind to:

sealed class Database : INotifyPropertyChanged
{
    //Declare Instance
    private static readonly Database instance = new Database();

    //Private Constructor
    private Database() { }

    //The entry point into this Database
    public static Database Instance
    {
        get
        {
            return instance;
        }
    }

    #region Collections corresponding with database tables

    public ObservableCollection<Category> Categories { get; set; }
    public ObservableCollection<CategoryType> CategoryTypes { get; set; }

And here is a sample of my XAML:

<ListBox x:Name="CategoriesListBox" Margin="0,0,-12,0" ItemsSource="{Binding Categories}" DisplayMemberPath="Name" />

In my page I have tried setting the data context as follows:

this.DataContext = Database.Instance;

However the binding does not work unless I explicitly set the ItemsSource in code as follows:

CategoriesListBox.ItemsSource = Database.Instance.Categories;

I know that I should be able to do this all declaratively, however I have tried many different ways of setting the ItemsSource declaratively (in addition to what I have detailed above) and none work.

Can someone help me out?

Further info: The output windows at runtime shows the following: System.Windows.Data Error: Cannot get ‘Categories’ value (type ‘System.Collections.ObjectModel.ObservableCollection`1[BTT.PinPointTime.Entities.Category]’) from ‘BTT.PinPointTime.WinPhone.Database’ (type ‘BTT.PinPointTime.WinPhone.Database’). BindingExpression: Path=’Categories’ DataItem=’BTT.PinPointTime.WinPhone.Database’ (HashCode=99825759); target element is ‘System.Windows.Controls.ListBox’ (Name=’CategoriesListBox’); target property is ‘ItemsSource’ (type ‘System.Collections.IEnumerable’).. System.MethodAccessException: Attempt to access the method failed: BTT.PinPointTime.WinPhone.Database.get_Categories()
at System.Reflection.RuntimeMethodInfo.InternalInvoke(Object obj, BindingFlags invokeAttr

Answer 1

I found out that the problem was related to the access level of my Database class. When I changed it from “sealed” to “public sealed” the databinding worked.

public sealed class Database : INotifyPropertyChanged
{
    //Declare Instance
    private static readonly Database instance = new Database();

    //Private Constructor
    private Database() 
    {
        //Categories = new ObservableCollection<Category>();
    }

   //more code here....