added alternate JsonContent for .NET Core

Author: ra0o0f

src/ArangoDB.Client/Http/HttpConnection.cs

@@ -106,7 +106,7 @@ public async Task<HttpResponseMessage> SendCommandAsync(HttpMethod method, Uri u
                 requestMessage.Content = new JsonContent(db, data);
             if (onStreamReady != null)
                 requestMessage.Content = new GenericStreamContent(db, onStreamReady);
-
+            
             var responseMessage = await httpClient.SendAsync(requestMessage).ConfigureAwait(false);
 
             if (db.LoggerAvailable)

src/ArangoDB.Client/Http/JsonContent.cs

@@ -13,13 +13,14 @@
 
 namespace ArangoDB.Client.Http
 {
+#if !NETSTANDARD1_1
     // from http://stackoverflow.com/questions/25335897/using-json-net-to-serialize-object-into-httpclients-response-stream
     public class JsonContent : HttpContent
     {
         IArangoDatabase db;
 
         object data { get; set; }
-        public JsonContent(IArangoDatabase db,object data)
+        public JsonContent(IArangoDatabase db, object data)
         {
             this.db = db;
             this.data = data;
@@ -43,15 +44,53 @@ protected override async Task SerializeToStreamAsync(Stream stream, TransportCon
                 var jsonWriter = new JsonTextWriter(streamWriter);
                 var serializer = docSerializer.CreateJsonSerializer();
                 serializer.Serialize(jsonWriter, data);
+
                 await streamWriter.FlushAsync().ConfigureAwait(false);
             }
         }
-
+        
         protected override bool TryComputeLength(out long length)
         {
-            //we don't know. can't be computed up-front
             length = -1;
             return false;
         }
     }
+#else
+    public class JsonContent : HttpContent
+    {
+        private readonly MemoryStream _Stream = new MemoryStream();
+
+        public JsonContent(IArangoDatabase db, object value)
+        {
+            var jw = new JsonTextWriter(new StreamWriter(_Stream));
+
+            var jObject = value as JObject;
+            if (jObject != null)
+            {
+                jObject.WriteTo(jw);
+            }
+            else
+            {
+                var docSerializer = new DocumentSerializer(db);
+                var serializer = docSerializer.CreateJsonSerializer();
+                serializer.Serialize(jw, value);
+            }
+            jw.Flush();
+            _Stream.Position = 0;
+        }
+        protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
+        {
+            _Stream.CopyTo(stream);
+            var tcs = new TaskCompletionSource<object>();
+            tcs.SetResult(null);
+            return tcs.Task;
+        }
+
+        protected override bool TryComputeLength(out long length)
+        {
+            length = _Stream.Length;
+            return true;
+        }
+    }
+#endif
 }