Binding to UserControl.Resource from within datatemplate created in Code (WPF) - wpf

Question

I want to reference my datacontext from inside a datatemplate. In XAML it works fine: I create a BindingProxy that is referenced as staticResource from inside the DataTemplate and so I can access the required property.
<UserControl.Resources>
<ResourceDictionary>
<helpers:BindingProxy x:Key="DataContextProxy" Data="{Binding}" />
</ResourceDictionary>
</UserControl.Resources>
<Grid>
<Grid.Resources>
<helpers:ComboBoxPerformanceConverter x:Key="AntriebsArtConverter" LookupDictionary="{Binding Source={StaticResource DataContextProxy}, Path=Data.AntriebsArtenDict }" />
</Grid.Resources>
...
<telerik:RadGridView ItemsSource="{Binding MyItemSource }">
<telerik:RadGridView.Columns>
<telerik:GridViewComboBoxColumn
ItemsSource="{Binding Source={StaticResource DataContextProxy}, Path=Data.AntriebsArten}"
DataMemberBinding="{Binding Fahrzeug.AntriebsArtId}"
SelectedValueMemberPath="AntriebsArtId"
DisplayMemberPath="Bezeichnung">
<telerik:GridViewComboBoxColumn.CellTemplate>
<DataTemplate>
<TextBlock Text="{Binding Fahrzeug.AntriebsArtId, Converter={StaticResource AntriebsArtConverter}}" />
</DataTemplate>
</telerik:GridViewComboBoxColumn.CellTemplate>
</telerik:GridViewComboBoxColumn>
</telerik:RadGridView.Columns>
...
If I try the same in Code I get everything working except the binding for LookupDictionary. Here I try to reference the datacontext not from the datagrid but from the surrounding UserControl. It gives me the error "Resource with name ""DataContextProxy"" cannot be found. any advice on how I could solve this?
Private Function CreateDataTemplate(textblockName As String) As DataTemplate
Dim memoryStream As MemoryStream
Dim parserContext As New ParserContext()
Dim xaml = "<DataTemplate xmlns:helpers=""clr-namespace:ViewModel.Helpers;assembly=ViewModel"">"
xaml += "<DataTemplate.Resources>"
xaml += "<helpers:ComboBoxPerformanceConverterVm x:Key=""AntriebsArtConverter"" LookupDictionary=""{Binding Path=Data.AntriebsArtenDict, Source={StaticResource DataContextProxy}}""/>"
xaml += "</DataTemplate.Resources><TextBlock Text=""{Binding Fahrzeug.AntriebsArtId, Converter={StaticResource AntriebsArtConverter}}"" /></DataTemplate>"
memoryStream = New MemoryStream(Encoding.UTF8.GetBytes(xaml))
parserContext.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation")
parserContext.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml")
Dim dataTemplate = CType(XamlReader.Load(memoryStream, parserContext), DataTemplate)
Return dataTemplate
End Function
Thanks for your help in advance!

Answer 1

In your xaml file, the helpers:ComboBoxPerformanceConverterVm is defined outside , its "DataContext" is the UserControl, and knows DataContextProxy.
But in the code, you moved this converter to inside the DataContext for this converter is now: "Column".
The best solution is to move this converter definition outside of like what you did in Xaml.