Expose itemsource property of controls inside a usercontrol

Question

I have a usercontrol containing some buttons and a ListView.

I want my custom control to have an ItemsSource property that binds to the listviews itemsource directly.

MyControl.xaml.cs

public partial class MyControl : UserControl
{

    public static DependencyProperty ItemsSourceProperty =
              ListView.ItemsSourceProperty.AddOwner(typeof(AddFilesControl));

    public ObservableCollection<DocumentFile> ItemsSource
    {
        get { return (ObservableCollection<DocumentFile>)GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty, value); }
    }
}

MyControl.xaml

<UserControl x:Class="[...].MyControls.MyControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008">
    <Grid>
        <ListView>
           <ListView.ItemTemplate>
              [...]
           </ListView.ItemTemplate>
        </ListView>
    </Grid>
</UserControl>

MyViewModel.cs (set as the DataSource of MyWindow containing only MyControl)

public class MyViewModel : INotifyPropertyChanged
{
    public ObservableCollection<DocumentFile> DefaultList { get; set; }
}

When debugging no items are displayed, but there are items in the ViewModel.

The Binding seems to be correct.

<custom:MyControl ItemsSource="{Binding DefaultList}" />

What is wrong here ?

I don't get why this should be offtopic. The problem is clear and so is the code I provided. (IMO) .. ?! — Felix D., May 28 '18 at 12:25
I asked a similar question a while ago, check it out: https://stackoverflow.com/questions/50352908/how-to-properly-expose-properties-of-internal-controls — Ruben Bohnet, May 28 '18 at 12:25
@RubenBohnet thanks. I've seen that. It's working for very well for the `SelectedItem`-Property. I got no idea why `ItemsSource` is not working. — Felix D., May 28 '18 at 12:27
the code you provided, isn't a [mcve] - it is not complete. where DP is used to display items? also in `ItemsSoure="{Binding DefaultList}"` property name is ItemsSoure, not ItemsSource — ASh, May 28 '18 at 12:48
@Ash that's just a spelling mistake. IMO it contains everything one could need to reproduce the issue. True - I could add some more xaml and a dummy viewmodel. But IMO it't too obvious what it would look like. — Felix D., May 28 '18 at 12:58
@FelixD., I repeat my previous question "where DP ItemsSource is used to display items?". It is declared and assigned, but not connected to view element — ASh, May 28 '18 at 13:06
@Ash Well I guess I did not implement it in the right way. the above is all I got. maybe thats already the source of the problem. Doesn't `ListView.ItemsSourceProperty.AddOwner` already links the ItemsSource to the listview in my control ? — Felix D., May 28 '18 at 13:11
`AddOwner` method has entirely different purpose. Binding can link the ItemsSource to the listview. — ASh, May 28 '18 at 13:13
@ASh could you provide an example ? I'm kinda confused how to bind and not use the datacontext that is provided for the custom-controls-parent ?! — Felix D., May 28 '18 at 13:15
As a note, a property of type `ObservableCollection` should not be called ItemsSource. It should just be `DocumentFiles` or something like that. You can't assign any kind of items. — Clemens, May 28 '18 at 16:48

score 2 · Accepted Answer · answered May 28 '18 at 13:22

ListView element which is a part of MyControl is not connected to MyControl.ItemsSource

that can be fixed by creating a binding:

<UserControl x:Class="[...].MyControls.MyControl"
             x:name="myControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008">
    <Grid>
        <ListView ItemsSource="{Binding ItemsSource, ElementName=myControl}">

        </ListView>
    </Grid>
</UserControl>

DP.AddOwner() method doesn't create a binding. ItemsSourceProperty DP is declared by ItemsControl class. AddOwner isn't aware about ListView in MyControl. How can it bind them together?

just came up with this by myself. thanks for ur efford ! I was missing that ! — Felix D., May 28 '18 at 13:23

Expose itemsource property of controls inside a usercontrol

1 Answers1