Question

In my code-behind I have the following in the class:

public ObservableCollection<int> ints;

Its value is initialized in the constructor:

ints = new ObservableCollection<int>();

I’m then binding a label to ints:

<Label Name="label" Content="{Binding Source={StaticResource ints}, Path=Count}"/>

After running the program, a XamlParseException occurs:

‘Provide value on ‘System.Windows.StaticResourceExtension’ threw an
exception.’ Line number ’12’ and line position ’20’.

I guess there is something wrong with the binding line. Any suggestions?

A complete demonstration program illustrating the issue follows:

XAML:

<Window x:Class="BindingObservableCollectionCountLabel.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">

    <DockPanel>            
        <StackPanel>
            <TextBox Name="textBox" Text="10"/>
            <Button Name="add" Click="add_Click" Content="Add"/>
            <Button Name="del" Click="del_Click" Content="Del"/>
            <Label Name="label" Content="{Binding Source={StaticResource ints}, Path=Count}"/>
        </StackPanel>            
    </DockPanel>
</Window>

C#:

using System;
using System.Windows;
using System.Collections.ObjectModel;

namespace BindingObservableCollectionCountLabel
{
    public partial class MainWindow : Window
    {
        public ObservableCollection<int> ints;

        public MainWindow()
        {
            InitializeComponent();

            ints = new ObservableCollection<int>();
        }

        private void add_Click(object sender, RoutedEventArgs e)
        {
            ints.Add(Convert.ToInt32(textBox.Text));
        }

        private void del_Click(object sender, RoutedEventArgs e)
        {
            if (ints.Count > 0) ints.RemoveAt(0);
        }
    }    
}

Answer 1

If having that collection in resources is not a requirement, do the following:

1. Change binding to

   <Label Name="label"
          Content="{Binding Path=ints.Count,
                            RelativeSource={RelativeSource AncestorType=Window}}"/>
   

2. Make ints a property:

   public ObservableCollection<int> ints { get; private set; }

If you need this collection to be a resource, change you window constructor to

public MainWindow()
{
    // line order is important!
    Resources.Add("ints", ints = new ObservableCollection<int>());
    InitializeComponent();
}

and leave XAML unchanged