Binding a property on on a great-grandchild to an ancestor

I'm not even sure how to express this, so im very sorry if the title is confusing.. My XAML (simplified) looks like this:

<UserControl x:Class="PBA.Application.Client.UserControls.UserControls.FreqReserve.OverView" xmlns:FreqReserve="clr-namespace:PBA.Application.Client.UserControls.UserControls.FreqReserve">
...
    <DockPanel>
        <UserControls:LegendControl>
            <UserControls:LegendControl.Items>
                <UserControls:LegendItem Visibility="{Binding Path=IsDirtyVisible, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type FreqReserve:OverView}}, Converter={StaticResource btvc}}" Identifier="Pink" Text="Ikke sendt"></UserControls:LegendItem>
                <UserControls:LegendItem Identifier="Yellow" Text="Sendt"></UserControls:LegendItem>
                <UserControls:LegendItem Identifier="LightGreen" Text="Accepteret"></UserControls:LegendItem>
                <UserControls:LegendItem Identifier="White" Text="Ikke accepteret"></UserControls:LegendItem>
            </UserControls:LegendControl.Items>
        </UserControls:LegendControl>
    </DockPanel>
</UserControl>

where the L开发者_高级运维egendItem list is templated inside the legendcontrol.

The binding expression fails with a System.Windows.Data Error: 4. I've tried using elementname instead, with the same results. I'm guessing it has something to do with the LegendItems not actually being directly in the Visual tree but i have no idea (WPF rookie, i know). What am i doing wrong?

You have a typo in the AncestorType. You want to say FreqReserve.OverView. Also, you are going to have to reference the library's namespace as defined in your UserControl.

Something like this:

<UserControl x:Class="PBA.Application.Client.UserControls.UserControls.FreqReserve.OverView"
             ...
             xmlns:local="clr-namespace:PBA.Application.Client.UserControls.UserControls">

    ...
       <DockPanel>
        <UserControls:LegendControl>
            <UserControls:LegendControl.Items>
                <UserControls:LegendItem IsVisible="{Binding Path=IsDirtyVisible, 
                    RelativeSource={RelativeSource Mode=FindAncestor, 
                                    AncestorType={x:Type local:FreqReserve.OverView}}}" 
                    Identifier="Pink" 
                    Text="Ikke sendt"></UserControls:LegendItem>

               ....         

        </UserControls:LegendControl>
    </DockPanel>
</UserControl>

Note that you will have to put the correct namespace for the "local" declaration, but you should get that from IntelliSense if you aren't sure what it should be.