From 11d8dc68eee165cf13ceede6c1f216b591e6672e Mon Sep 17 00:00:00 2001
From: Anne Erdtsieck <anne.erdtsieck@topicus.nl>
Date: Thu, 6 Feb 2025 16:53:50 +0100
Subject: [PATCH] Cast based on StreamIdentity

---
 .../Events/Aggregation/CustomProjection.cs       | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/src/Marten/Events/Aggregation/CustomProjection.cs b/src/Marten/Events/Aggregation/CustomProjection.cs
index 9096dc506b..0c9509b583 100644
--- a/src/Marten/Events/Aggregation/CustomProjection.cs
+++ b/src/Marten/Events/Aggregation/CustomProjection.cs
@@ -376,7 +376,7 @@ async ValueTask<TDoc> ILiveAggregator<TDoc>.BuildAsync(IReadOnlyList<IEvent> eve
         var documentSessionBase = session as DocumentSessionBase ?? (DocumentSessionBase)session.DocumentStore.LightweightSession();
 
         var latestEvent = events.Last();
-        var streamId = IdentityFromEvent(latestEvent);
+        var streamId = IdentityFromEvent(documentSessionBase.Options.EventGraph.StreamIdentity, latestEvent);
         var slice = new EventSlice<TDoc, TId>(streamId, session, events);
         if (Lifecycle == ProjectionLifecycle.Live)
         {
@@ -420,16 +420,6 @@ public IAggregateCache<TId, TDoc> CacheFor(Tenant tenant)
         }
     }
 
-    public TId IdentityFromEvent(IEvent e)
-    {
-        if (typeof(TId) == typeof(Guid))
-        {
-            return e.StreamId.To<TId>();
-        }
-
-        return e.StreamKey.To<TId>();
-    }
+    public TId IdentityFromEvent(StreamIdentity streamIdentity, IEvent e) =>
+        streamIdentity == StreamIdentity.AsGuid ? e.StreamId.To<TId>() : e.StreamKey.To<TId>();
 }
-
-
-