Xamarin DataTemplateSelector TargetType

MultiDataTemplateSelector.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Linq;
using System.Reflection;

namespace Xamarin.Forms
{
  [ContentProperty(nameof(Templates))]
  public class MultiDataTemplateSelector : DataTemplateSelector
  {
    public IList<TypedDataTemplate> Templates { get; } = new ObservableCollection<TypedDataTemplate>();

    public MultiDataTemplateSelector()
    {
      var incc = (INotifyCollectionChanged)Templates;
      incc.CollectionChanged += (sender, e) =>
      {
        if (e?.NewItems.Cast<TypedDataTemplate>()
            .Any(tdt => tdt?.TargetType == null || tdt?.Template == null) == true)
          throw new InvalidOperationException("All items must have all properties set.");
      };
    }

    protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
    {
      if (item == null) return null;
      if (!Templates.Any()) throw new InvalidOperationException("No DataTemplates found.");

      var result =
        Templates.FirstOrDefault(t => t.TargetType.GetTypeInfo().IsAssignableFrom(item.GetType().GetTypeInfo()));
      if (result == null)
        throw new ArgumentOutOfRangeException($"Could not find a matching template for type '{item.GetType()}'.");

      return result.Template;
    }
  }

  [ContentProperty(nameof(Template))]
  public class TypedDataTemplate
  {
    public Type TargetType { get; set; }
    public DataTemplate Template { get; set; }
  }
}