The DataContext of each row in your GridView is going to be an item in the ItemSource of the GridView... your binding may be looking for a property called Count on each item in the ObservableCollection rather than collection itself.
The binding you have will work if you want the Count property of each item, otherwise, you need to use a RelativeSource binding to get from the DataContext of the GridView row in question back to the ItemsSource of the GridView itself.
XAML
<ListView ItemsSource="{Binding AllItems}">
<ListView.View>
<GridView>
<GridViewColumn Header="Name" DisplayMemberBinding="{Binding Name}" ></GridViewColumn>
<GridViewColumn Header="IsSelected" DisplayMemberBinding="{Binding IsSelected}" ></GridViewColumn>
<GridViewColumn Header="AllItems.MyItems.Count" DisplayMemberBinding="{Binding MyItems.Count}" ></GridViewColumn>
<GridViewColumn Header="GridView.ItemsSource.Count" DisplayMemberBinding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListView}}, Path=ItemsSource.Count}" ></GridViewColumn>
</GridView>
</ListView.View>
</ListView>
CODE
public partial class Window1 : Window
{
public ObservableCollection<SillyClass> AllItems { get; set; }
public Window1()
{
InitializeComponent();
AllItems = new ObservableCollection<SillyClass>()
{
new SillyClass()
{
Name = "Matt",
MyItems = new List<string>() { "Item 1", "Item 2"}
},
new SillyClass()
{
Name = "Jesper",
IsSelected = true,
MyItems = new List<string>() { "Item 1", "Item 2", "Item 3"}
},
};
this.DataContext = this;
}
}
public class SillyClass
{
public string Name {get; set;}
public bool IsSelected {get; set;}
public List<string> MyItems { get; set; }
}
Warm Regards,
Matt
