ItemTemplate BindingContext

Has anyone had an issue with the ItemTemplate BindingContext NOT being set to an item in ItemsSource? I have the following code:

<ListView Grid.Row="0" Grid.Column="0" ItemsSource="{Binding MyItemCollection}">
        <ListView.ItemTemplate>
             <DataTemplate>
               <TextCell Text="{Binding ItemName}"/>
             </DataTemplate>
        </ListView.ItemTemplate>
  </ListView>

I get an error saying "ItemName" is not found on "MainViewModel" (Page's ViewModel). Why is TextCell's BindingContext not an item in "MyItemCollection" (ObservableCollection)?

Thanks