public class CompositeType

    {

        public CompositeType()

        {

            SubCompositeTypes = new List<SubCompositeType>() { new SubCompositeType() };

        }

        public bool BoolValue { get; set; }

        public string StringValue { get; set; }

        public List<SubCompositeType> SubCompositeTypes

        {

            get;

            set;

        }

    }

    public class SubCompositeType

    {

        bool boolValue = true;

        string stringValue = "Hello ";

        public bool BoolValue

        {

            get { return boolValue; }

            set { boolValue = value; }

        }

        public string StringValue

        {

            get { return stringValue; }

            set { stringValue = value; }

        }

    }

#region JosnPost

            CompositeType compositeType = new CompositeType

            {

                StringValue = "1",

                BoolValue = false

            };

            DataContractJsonSerializer dcSerializer = new DataContractJsonSerializer(typeof(CompositeType));

            MemoryStream stream = new MemoryStream();

            dcSerializer.WriteObject(stream, compositeType);

            string data = Encoding.UTF8.GetString(stream.ToArray(), 0, (int)stream.Length);

            //HttpClient client = new HttpClient();

            //client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            string link = "http://localhost:1766/Service1.svc/CreateUser";

            //HttpResponseMessage respondse = await client.PostAsync(link, new StringContent(data));

            //string dataWithJason = await respondse.Content.ReadAsStringAsync();

            var request = (HttpWebRequest)WebRequest.Create(new Uri(link));

            request.ContentType = "application/json";

            request.Method = "POST";

            using (var requestStream = await request.GetRequestStreamAsync())

            {

                var writer = new StreamWriter(requestStream);

                writer.Write(data);

                writer.Flush();

            }

            using (var resp = await request.GetResponseAsync())

            {

                using (var responseStream = resp.GetResponseStream())

                {

                    var reader = new StreamReader(responseStream);

                    var result = reader.ReadToEnd();

                }

            }

[OperationContract]

        [WebInvoke(

            UriTemplate = "CreateUser",

            RequestFormat = WebMessageFormat.Json,

            ResponseFormat = WebMessageFormat.Json,

            Method = "POST")]

        string CreateUser(CompositeType compositeType);

public string CreateUser(CompositeType compositeType)

        {

            return "OK" + compositeType.StringValue + " " + compositeType.BoolValue + " " + compositeType.SubCompositeTypes.FirstOrDefault().StringValue;

        }

<system.serviceModel>

    <services>

      <service behaviorConfiguration="MyServiceBehavior" name="Server.Service1">

        <endpoint address="" binding="webHttpBinding" behaviorConfiguration="web" contract="Server.IService1">

          <identity>

            <dns value="localhost"/>

          </identity>

        </endpoint>

        <endpoint address="max" binding="mexHttpBinding" contract="IMetadataExchange"></endpoint>

      </service>

    </services>

    <behaviors>

      <endpointBehaviors>

        <behavior name ="web">

          <webHttp />

        </behavior>

      </endpointBehaviors>

      <serviceBehaviors>

        <behavior name="MyServiceBehavior">

          <!-- To avoid disclosing metadata information, set the values below to false before deployment -->

          <serviceMetadata httpGetEnabled="true" httpsGetEnabled="true"/>

          <!-- To receive exception details in faults for debugging purposes, set the value below to true.  Set to false before deployment to avoid disclosing exception information -->

          <serviceDebug includeExceptionDetailInFaults="false"/>

        </behavior>

      </serviceBehaviors>

    </behaviors>

    <protocolMapping>

      <add binding="basicHttpsBinding" scheme="https" />

    </protocolMapping>

    <serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true" />

  </system.serviceModel>