diff --git a/ServiceLayer/PostServices/DetailPostDto.cs b/ServiceLayer/PostServices/DetailPostDto.cs
index 005de7b..1f6d160 100644
--- a/ServiceLayer/PostServices/DetailPostDto.cs
+++ b/ServiceLayer/PostServices/DetailPostDto.cs
@@ -93,7 +93,7 @@ public class DetailPostDto : ILinkToEntity<Post>
         /// </summary>
         public DateTime LastUpdatedUtc { get { return DateTime.SpecifyKind(LastUpdated, DateTimeKind.Utc); } }
 
-        public string TagNames { get { return string.Join(", ", Tags.Select(x => x.Name)); } }
+        public string TagNames { get { return Tags == null ? string.Empty : string.Join(", ", Tags.Select(x => x.Name)); } }
 
         //ctor
         public DetailPostDto()
diff --git a/ServiceLayer/PostServices/DetailPostDtoAsync.cs b/ServiceLayer/PostServices/DetailPostDtoAsync.cs
index c133b32..bf20784 100644
--- a/ServiceLayer/PostServices/DetailPostDtoAsync.cs
+++ b/ServiceLayer/PostServices/DetailPostDtoAsync.cs
@@ -92,7 +92,7 @@ public class DetailPostDtoAsync : ILinkToEntity<Post>
         /// </summary>
         public DateTime LastUpdatedUtc { get { return DateTime.SpecifyKind(LastUpdated, DateTimeKind.Utc); } }
 
-        public string TagNames { get { return string.Join(", ", Tags.Select(x => x.Name)); } }
+        public string TagNames { get { return Tags == null ? string.Empty : string.Join(", ", Tags.Select(x => x.Name)); } }
 
         //ctor
         public DetailPostDtoAsync()