具有自定义对象输入的wcf方法

我有一个方法,它接收自定义对象作为输入。

[OperationContract(Name = "MyMethod")]
public CustomOutput MyMethod(CustomInput inp){}

[DataContract(Namespace = "")]
    public class CustomInput 
    {
        [DataMember(Name = "x")]
        public string x { get; set; }
    }

我从控制台应用程序调用它:

[DataContract(Namespace = "")]
public class CustomInput 
{
    [DataMember(Name = "x")]
    public string x { get; set; }
}   

class Program { 
private const string URL2 = "http://.../MyMethod";

    static void Main(string[] args)
    {
        HttpClient client = new HttpClient();
        string str = JsonConvert.SerializeObject(new CustomInput () { x = "pippo" });
        HttpContent content = new StringContent(str, Encoding.UTF8, "application/json");
        HttpResponseMessage response = client.PostAsync(URL2, content).Result;  // Blocking call!
        if (response.IsSuccessStatusCode)
        {
        }
        else
        {
            Console.WriteLine("{0} ({1})", (int)response.StatusCode, response.ReasonPhrase);
        }
    } 
}

有了这段代码,我可以在服务器上正确调用mymethod,但custominput始终为空。
有什么建议吗?