WPF: bind property from MainWindow.xaml cause an error - wpf

Question

So I have this view model:
public class WiresharkFiles : INotifyPropertyChanged
{
public ObservableCollection<WiresharkFile> List { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
private bool _inUse;
private int _packets;
private bool _hasItems;
public WiresharkFiles()
{
List = new ObservableCollection<WiresharkFile>();
HasItems = false;
List.CollectionChanged += List_CollectionChanged;
}
private void List_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
HasItems = List.Count > 0;
}
public bool InUse
{
get { return _inUse; }
set
{
_inUse = value;
NotifyPropertyChanged("InUse");
}
}
public int Packets
{
get { return _packets; }
set
{
_packets = value;
NotifyPropertyChanged("Packets");
}
}
public bool HasItems
{
get { return _hasItems; }
set
{
_hasItems = value;
NotifyPropertyChanged("HasItems");
}
}
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
MainWindow.xaml
private WiresharkFiles caps;
public MainWindow()
{
InitializeComponent();
caps = new WiresharkFiles();
}
Window.Resources
<Window.Resources>
<Convertors:CollectionHasItemsConverter x:Key="CollectionHasItemsConverter"/>
</Window.Resources>
Converter
public class CollectionHasItemsConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return (bool)value;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
And base of my collection item (empty or not) i want to enable/disable my Button:
<Button Name="btnDeleteAll"
Click="btnDeleteAll_Click"
IsEnabled="{Binding Path=(caps.HasItems),Converter={StaticResource CollectionHasItemsConverter}}">
And i got this error:
XamlParseException: Type reference cannot find type named
'{http://schemas.microsoft.com/winfx/2006/xaml/presentation}caps'.

Answer 1

I don't see where you're associating your DataContext with the caps property.
Make sure you have a public property because the WPF engine isn't running from within your class and won't be able to access the private WiresharkFiles caps; variable. Try the following:
private WiresharkFiles caps;
public WiresharkFiles Files { get { return caps; } }
with a corresponding
public MainWindow()
{
InitializeComponent();
caps = new WiresharkFiles();
DataContext = Files;
}
Your XAML will then bind to Files as follows
IsEnabled="{Binding Path=HasItems}"
Update You'll need to have a look at implementing and binding to commands for the button which will make it a lot better. Look at this article for info on implementing and dealing with commands.

Answer 2

caps is a private variable:
private WiresharkFiles caps;
In order to bind, it would have to be a public property:
public WiresharkFiles caps {get;set;}
You would also have to set the datacontext of the window to itself. Something like:
this.DataContext = this;
or
In your window tag put:
DataContext="{Binding RelativeSource={RelativeSource Self}}"
I don't see how this relates to your initial question but you can use dot notation in binding.
You can bind:
{Binding AnObservableCollection.Count}
And you can compare that to 0 in a datatrigger. With a button and a bound command if you want to disable it then I'd use the canexecute of icommand and return false if you have no entries or whatever your logic is.