diff --git a/server/AyaNova/Controllers/WorkOrderController.cs b/server/AyaNova/Controllers/WorkOrderController.cs
index ab93b353..9d47860f 100644
--- a/server/AyaNova/Controllers/WorkOrderController.cs
+++ b/server/AyaNova/Controllers/WorkOrderController.cs
@@ -158,10 +158,13 @@ namespace AyaNova.Api.Controllers
 
         /// <summary>
         /// Put (update) WorkOrder
+        /// This route does not update the entire WorkOrder object graph, only the top level
+        /// in other words nothing in any descendent child collections such as WorkOrderItems and below.
+        /// Use the separate routes to update descendents of the WorkOrder
         /// </summary>
-        /// <param name="id"></param>
-        /// <param name="updatedObject"></param>
-        /// <returns></returns>
+        /// <param name="id">WorkOrder id</param>
+        /// <param name="updatedObject">Workorder top level only, no descendents are evaluated</param>
+        /// <returns>New concurrency token</returns>
         [HttpPut("{id}")]
         public async Task<IActionResult> PutWorkOrder([FromRoute] long id, [FromBody] WorkOrder updatedObject)
         {
@@ -178,8 +181,13 @@ namespace AyaNova.Api.Controllers
             if (!Authorized.HasModifyRole(HttpContext.Items, biz.BizType))
                 return StatusCode(403, new ApiNotAuthorizedResponse());
 
-            biz.PutAsync(id, updatedObject);
-//todo: handle concurrency in biz object, what to do?
+            var o = await biz.PutAsync(id, updatedObject);
+            if (o == null)
+                return BadRequest(new ApiErrorResponse(biz.Errors));
+                
+            return Ok(ApiOkResponse.Response(new { ConcurrencyToken = o.ConcurrencyToken }, true));
+
+            //todo: handle concurrency in biz object, what to do?
 
             // var o = await biz.PutAsync(id, updatedObject);
             // try
@@ -285,7 +293,7 @@ namespace AyaNova.Api.Controllers
                 return BadRequest(new ApiErrorResponse(biz.Errors));
             else
                 return CreatedAtAction(nameof(WorkOrderController.GetWorkOrderItem), new { id = o.Id, version = apiVersion.ToString() }, new ApiCreatedResponse(o));
-            
+
         }
 
 
diff --git a/server/AyaNova/biz/WorkOrderBiz.cs b/server/AyaNova/biz/WorkOrderBiz.cs
index 0027d350..4c8a8092 100644
--- a/server/AyaNova/biz/WorkOrderBiz.cs
+++ b/server/AyaNova/biz/WorkOrderBiz.cs
@@ -152,25 +152,21 @@ namespace AyaNova.Biz
             if (HasErrors)
                 return null;
 
-            //  try
-            //             {
-            //                 if (o==null)
-            //                     return BadRequest(new ApiErrorResponse(biz.Errors));
-            //             }
-            //             catch (DbUpdateConcurrencyException)
-            //             {
-            //                 if (!await biz.ExistsAsync(id))
-            //                     return NotFound(new ApiErrorResponse(ApiErrorCode.NOT_FOUND));
-            //                 else
-            //                     return StatusCode(409, new ApiErrorResponse(ApiErrorCode.CONCURRENCY_CONFLICT));
-            //             }
-
-
-            //Log event and save context          
+            try
+            {
+                await ct.SaveChangesAsync();
+            }
+            catch (DbUpdateConcurrencyException)
+            {
+                if (!await WorkOrderExistsAsync(id))
+                    AddError(ApiErrorCode.NOT_FOUND);
+                else
+                    new ApiErrorResponse(ApiErrorCode.CONCURRENCY_CONFLICT);
+                return null;
+            }
             await EventLogProcessor.LogEventToDatabaseAsync(new Event(UserId, dbObject.Id, BizType, AyaEvent.Modified), ct);
             await SearchIndexAsync(dbObject, false);
             await TagUtil.ProcessUpdateTagsInRepositoryAsync(ct, dbObject.Tags, SnapshotOfOriginalDBObj.Tags);
-
             return dbObject;
         }