WPF ComboBoxAdaptor does not display the ComboBox property - wpf

Question

https://stackoverflow.com/a/36192552/9387175
In this answer the user suggests that the comboBoxAdaptor can be used to add an item to a combo box even if it does not exist in the item source. I do in fact see that it is working in the code, but I can't figure out why it refuses to display. The normal combo box functions correctly in the below example, the comboBoxAdaptor is not visible. Am I missing something like styles or templates? I can't seem to find the right combination.
My xaml:
<Window x:Class="WpfApp1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:adapters="clr-namespace:WpfApp1.Adapters"
mc:Ignorable="d"
Title="MainWindow"
Height="200"
Width="650">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="210" />
<ColumnDefinition Width="210" />
</Grid.ColumnDefinitions>
<adapters:ComboBoxAdaptor Grid.Column="0"
AllowNull="False"
Height="80"
ItemsSource="{Binding Path=DataEntries}"
SelectedItem="{Binding Path=DataEntry}">
<ComboBox Height="80" />
</adapters:ComboBoxAdaptor>
<ComboBox Grid.Column="1"
Height="80"
ItemsSource="{Binding Path=DataEntries}"
SelectedItem="{Binding Path=DataEntry}"
DisplayMemberPath="Name"
SelectedValuePath="Name" />
</Grid>
</Window>
My Code:
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;
namespace WpfApp1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
SampleViewModel vm = new SampleViewModel();
DataContext = vm;
}
}
public class SampleDataClass
{
public string Name { get; set; }
public SampleDataClass(string name)
{
Name = name;
}
}
public class SampleViewModel : INotifyPropertyChanged
{
private readonly IList<SampleDataClass> _dataEntries;
private string _dataEntry;
public event PropertyChangedEventHandler PropertyChanged;
public SampleViewModel()
{
IList<SampleDataClass> list = new List<SampleDataClass>();
list.Add(new SampleDataClass("tools"));
list.Add(new SampleDataClass("set"));
list.Add(new SampleDataClass("sort"));
list.Add(new SampleDataClass("flap"));
_dataEntries = list;
}
public IList<SampleDataClass> DataEntries
{
get { return _dataEntries; }
}
public string DataEntry
{
get
{
return _dataEntry;
}
set
{
if (_dataEntry == value) {return;}
_dataEntry = value;
OnPropertyChanged("DataEntry");
}
}
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}

Answer 1

Turns out that I was missing the style that links the ComboBox to the content of the ContentControl (ComboBoxAdaptor)
Style Example
<Style TargetType="adapters:ComboBoxAdaptor">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="adapters:ComboBoxAdaptor">
<ContentPresenter Content="{TemplateBinding ComboBox}"
Margin="{TemplateBinding Padding}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>