How to use Xamarin DataTemplateSelector with DataTemplates organized in folders?

Question

I'm trying to implement something like this MS Docs sample, with the DataTemplates as separate files: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/templates/data-templates/selector

My folder structure...

Project
 |
 └─ Views\
     |  MyView.xaml
     |
     └───DataTemplates\
           DT1.xaml (no .cs)
           DT2.xaml (no .cs)
           DTSelector.cs

From MyView.xaml...

<ContentPage ...             
    xmlns:datatemplates="clr-namespace: Project.Views.DataTemplates"/>
<ContentPage.Resources>
    <ResourceDictionary>

        <ResourceDictionary.MergedDictionaries>       
            <datatemplates:DT1/> 
            <datatemplates:DT2/>
            <!-- This is the x:Key name, right? -->
            <!-- Intellisense can't find these  -->
        </ResourceDictionary.MergedDictionaries>

        <datatemplates:DTSelector x:Key="dTSelector"        
            DT1= "{StaticResource dT1}"
            DT2= "{StaticResource dT2}"/> 

    </ResourceDictionary>

From a DataTemplate...

<?xml version="1.0" encoding="utf-8" ?>
<ResourceDictionary xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">    
    <!-- x:Class has been removed -->
    <DataTemplate x:Name="DT1" x:Key="dT1">
        <Grid, etc...

DataTemplateSelector...

public class DTSelector: DataTemplateSelector
{    
    public DataTemplate DT1{ get; set; }
    public DataTemplate DT2{ get; set; }

    protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
    {    
        switch (App.CurrentUser.SomeEnum)
        {
            case SomeEnum.Pref1:
                 return DT1;
                 break;
            case SomeEnum.Pref2:
                return DT2;
                break;
            default:
                return DT1;
        }
    }
}

I have wrestled the code into the App level and got it to compile, but then DTSelector's always returns a null object, and it throws an exception. I'd prefer it at the page level, anyhow. It seems like there should be a... ResourceDictionary Source="DT1.xaml" x:Key="DT1" but that's not valid.

I assume MyView can't find the templates via xmlns because Intellisense only sees cs files... but I get a green squiggle and compilation error XLS0414: "The type 'datatemplates:DT1' not found..."

GitRepo here, for your pleasure: https://github.com/BullCityCabinets/DataTemplateSelectorExample201014

Thanks for any help!

Answer 1

I found if you put the DT1.xaml and MyView.xaml in the same folder. You can reference the resource dictionary by :

<ContentPage.Resources>

    <ResourceDictionary Source="DT1.xaml" />
    <ResourceDictionary Source="DT2.xaml" />

    <datatemplates:DTSelector x:Key="dTSelector"        
            DT1ref = "{StaticResource DT1key}"
            DT2ref = "{StaticResource DT2key}"/>

</ContentPage.Resources>

And the folder:

Refer: merge-local-resource-dictionaries