Created a small test for issue #23

RestSharp.Portable.Test/IssueTests.cs

@@ -2,8 +2,11 @@
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Net.Http;
+using System.Reflection;
 using System.Threading.Tasks;
 
+using Newtonsoft.Json;
+
 using Xunit;
 
 namespace RestSharp.Portable.Test
@@ -91,11 +94,47 @@ public void TestIssue19()
             }
         }
 
+        [Fact(DisplayName = "Issue 23")]
+        public async Task TestIssue23()
+        {
+            using (var client = new RestClient("http://httpbin.org/"))
+            {
+                var req = new RestRequest("/post", HttpMethod.Post);
+                var param = new Parameter
+                    {
+                        Value = new
+                            {
+                                Parameter1 = "param1",
+                            },
+                        Type = ParameterType.RequestBody,
+                    };
+
+                {
+                    var content = req.GetBodyContent(param);
+                    var s = await content.ReadAsStringAsync();
+                    Assert.Equal("{\"Parameter1\":\"param1\"}", s);
+                }
+
+                {
+                    req.AddBody(param.Value);
+                    var content = client.GetContent(req);
+                    var s = await content.ReadAsStringAsync();
+                    Assert.Equal("{\"Parameter1\":\"param1\"}", s);
+                }
+
+                var response = await client.Execute<PostResponse>(req);
+                var responseJson = JsonConvert.SerializeObject(response.Data.Json, Formatting.None);
+                Assert.Equal("{\"Parameter1\":\"param1\"}", responseJson);
+            }
+        }
+
         // ReSharper disable once ClassNeverInstantiated.Local
         [SuppressMessage("ReSharper", "UnusedAutoPropertyAccessor.Local", Justification = "ReSharper bug")]
         private class PostResponse
         {
             public Dictionary<string, string> Form { get; set; }
+
+            public object Json { get; set; }
         }
     }
 }