addresses an issue with polling

- when multiple rcc used on the same page items fails to subscribe for polling if rcc rendered shadow control for a twinelement

src/AXSharp.blazor/src/AXSharp.Presentation.Blazor.Controls/RenderableContent/RenderableContentControl.razor.cs

@@ -115,8 +115,9 @@ protected override void OnParametersSet()
 
         private void SubscribeForPolling(IRenderableComponent component, ITwinElement element)
         {
-            if (_pollingStarted) return;
+            if (this.Presentation.StartsWith("Shadow")) return;
             if (component == null) return;
+            if(PolledComponents.Contains(component)) return;
             PolledComponents?.Add(component);
             component?.AddToPolling(element, this.PollingInterval);
             _pollingStarted = true;
@@ -126,7 +127,7 @@ private void UnSubscribeFromPolling()
         {
             foreach (var renderableComponent in PolledComponents)
             {
-                renderableComponent.RemovePolledElements();
+                renderableComponent?.RemovePolledElements();
             }
 
             _pollingStarted = false;

src/sanbox/integration/ix-integration-blazor/Pages/ShadowProperties.razor

@@ -1,7 +1,10 @@
 @page "/ShadowProperties"
 
 <RenderableContentControl Presentation="ShadowControl"
-                   Context="@Entry.Plc.all_primitives" />
+                          Context="@Entry.Plc.all_primitives" />
+
+<RenderableContentControl Presentation="Control"
+                          Context="@Entry.Plc.all_primitives" PollingInterval="250" />