asp.net – 服务栈：类型定义应该以'{‘开头,期望序列化类型

我在我的asp.net应用程序中使用以下代码：

<asp:Button ID="btnAuth" runat="server" OnClick="btnAuth_Click" Text="Authenticate"/>

我在代码隐藏文件中的clien.Post方法上收到异常.

protected void btnAuth_Click(object sender,EventArgs e)
        {
            try
            {                
                var baseUrl = Request.Url.GetLeftPart(UriPartial.Authority) + "/api";
                var client = new JsonServiceClient(baseUrl);
                var authResponse = client.Post<AuthResponse>(new Auth { UserName = "admin",Password = "12345" });
                if (authResponse.ResponseStatus.ErrorCode == null)
                {
                   //Do Something here
                }
            }
            catch (WebServiceException ex)
            {
                throw ex;
            }
        }

Followin是我在clien.Post方法上收到的Exeception Detail：

[SerializationException: Type definitions should start with a '{',expecting serialized type 'AuthResponse',got string starting with: