Implement result getter

Hcs.Broker/Api/Request/Adapter/IErrorMessage.cs

@@ -5,5 +5,7 @@
         string ErrorCode { get; }
 
         string Description { get; }
+
+        string StackTrace { get; }
     }
 }

Hcs.Broker/Api/Request/NsiCommon/ExportNsiItemRequest.cs

@@ -1,4 +1,5 @@
-using Hcs.Broker.Internal;
+using Hcs.Broker.Api.Request.Adapter;
+using Hcs.Broker.Internal;
 using Hcs.Service.Async.NsiCommon;
 
 namespace Hcs.Broker.Api.Request.NsiCommon
@@ -36,17 +37,29 @@ namespace Hcs.Broker.Api.Request.NsiCommon
                 ListGroup = listGroup
             };
 
-            return await StartSendAsync(request, async asyncClient =>
+            return await SendAsync(request, async asyncClient =>
             {
                 var response = await asyncClient.exportNsiItemAsync(CreateRequestHeader(), request);
                 return response.AckRequest.Ack;
             }, token);
         }
 
-        internal async Task<NsiItemType?> GetResultAsync(string messageGuid)
+        internal async Task<RequestSingleResult<NsiItemType>> GetResultAsync(string messageGuid)
         {
             var result = await ExecuteGetResultAsync(messageGuid);
-            return result?.Item as NsiItemType;
+            if (result == null)
+            {
+                return RequestSingleResult<NsiItemType>.CreateNotReady();
+            }
+            if (result.Item is NsiItemType nsiItem)
+            {
+                return RequestSingleResult<NsiItemType>.CreateSuccessful(nsiItem);
+            }
+            else if (result.Item is IErrorMessage errorMessage)
+            {
+                return RequestSingleResult<NsiItemType>.CreateFailed(errorMessage);
+            }
+            return RequestSingleResult<NsiItemType>.CreateFailed(null);
         }
     }
 }

Hcs.Broker/Api/Request/RequestBase.cs

@@ -149,7 +149,7 @@ namespace Hcs.Broker.Api.Request
             }
         }
 
-        protected async Task<string> StartSendAsync(
+        protected async Task<string> SendAsync(
             object request,
             Func<TAsyncClient, Task<TAck>> sender,
             CancellationToken token)

Hcs.Broker/Api/Request/RequestSingleResult.cs

@@ -0,0 +1,43 @@
+using Hcs.Broker.Api.Request.Adapter;
+
+namespace Hcs.Broker.Api.Request
+{
+    public class RequestSingleResult<T>
+    {
+        public bool Ready { get; set; }
+
+        public bool Success { get; set; }
+
+        public T? Result { get; set; }
+
+        public IErrorMessage? ErrorMessage { get; set; }
+
+        public static RequestSingleResult<T> CreateNotReady()
+        {
+            return new RequestSingleResult<T>
+            {
+                Ready = false
+            };
+        }
+
+        public static RequestSingleResult<T> CreateSuccessful(T result)
+        {
+            return new RequestSingleResult<T>
+            {
+                Ready = true,
+                Success = true,
+                Result = result
+            };
+        }
+
+        public static RequestSingleResult<T> CreateFailed(IErrorMessage? errorMessage)
+        {
+            return new RequestSingleResult<T>
+            {
+                Ready = true,
+                Success = false,
+                ErrorMessage = errorMessage
+            };
+        }
+    }
+}