Make it possible to feed in options to the Enumerate handler

Toolkit.Foundation/Enumerate.cs

@@ -1,3 +1,23 @@
 namespace Toolkit.Foundation;
 
-public record Enumerate<TValue>(object? Key = null);
+public record Enumerate<TValue> : IEnumerate
+{
+    public object? Key { get; init; }
+
+    public static Enumerate<TValue, TOptions> With<TOptions>(TOptions options) where TOptions : class
+    {
+        return new Enumerate<TValue, TOptions>(options);
+    }
+}
+
+public interface IEnumerate
+{
+    object? Key { get; init; }
+}
+
+
+public record Enumerate<TValue, TOptions>(TOptions? Options = null) : IEnumerate
+    where TOptions : class
+{
+    public object? Key { get; init; }
+}

Toolkit.Foundation/ObservableCollectionViewModel.cs

@@ -97,7 +97,7 @@ public partial class ObservableCollectionViewModel<TViewModel> :
 
     public TViewModel this[int index]
     {
-        get => Count > 0 ? collection[index] : default;
+        get => collection[index];
         set => SetItem(index, value);
     }
 
@@ -299,21 +299,30 @@ public partial class ObservableCollectionViewModel<TViewModel> :
 
     public async Task Initialize()
     {
-        if (isInitialized)
+        if (IsInitialized)
         {
             return;
         }
 
-        isInitialized = true;
+        IsInitialized = true;
+        await Enumerate();
+    }
+
+    public async Task Enumerate()
+    {
+        Clear();
 
         object? key = this.GetAttribute<NotificationAttribute>()
             is NotificationAttribute attribute
             ? this.GetPropertyValue(() => attribute.Key) is { } value ? value : attribute.Key
             : null;
 
-        await Publisher.PublishUI(new Enumerate<TViewModel>(key));
+        await Publisher.PublishUI(CreateEnumeration(key));
     }
 
+    protected virtual IEnumerate CreateEnumeration(object? key) => 
+        new Enumerate<TViewModel>() with { Key = key };
+
     public void Insert(int index, TViewModel item) =>
         InsertItem(index, item);
 

Toolkit.Foundation/Selected.cs

@@ -1,6 +1,6 @@
 namespace Toolkit.Foundation;
 
-public record Selected<TValue>(TValue Value);
+public record Selected<TValue>(TValue? Value);
 
 public record Selected
 {

Toolkit.Foundation/SubscriptionManager.cs

@@ -5,6 +5,7 @@ public class SubscriptionManager(SubscriptionCollection subscriptions) :
 {
     public IEnumerable<object?> GetHandlers(Type notificationType, object key)
     {
+        var d = subscriptions;
         if (subscriptions.TryGetValue($"{(key is not null ? $"{key}:" : "")}{notificationType}",
             out List<WeakReference>? subscribers))
         {