Docusign Listener Argument Null（开发沙箱）

我在C＃网络服务中创建了一个网络方法，当信封状态更改时，该方法侦听Docusign调用：

[WebMethod]

        public void DocuSignConnectUpdate(DocuSignEnvelopeInformation DocuSignEnvelopeInformation)
        {
            
            //Check if null
            if (DocuSignEnvelopeInformation == null)
            {
                File.WriteAllText("C:\\websites\\DataAPI\\datalog.txt", "Data: " + "Data is null");
            }
            else
            {
                string envelopeId = "";
                try
                {
                    //Write a line in a file
                    File.WriteAllText("C:\\websites\\DataAPI\\datalog.txt", "Data: " + DocuSignEnvelopeInformation.ToString());
     
                    //Get some data out
                    envelopeId = DocuSignEnvelopeInformation.EnvelopeStatus.EnvelopeID;

                    //Write Data to a file
                    File.WriteAllText("C:\\websites\\DataAPI\\innerdatalog.txt", "Data: " + DocuSignEnvelopeInformation.ToString());


                }
                catch (Exception ex)
                {
                    // could not serialize
                    File.WriteAllText("C:\\websites\\DataAPI\\errorlog.txt", "Exception: " + ex.Message);
                    
                    throw new SoapException(ex.Message, SoapException.ClientFaultCode);
                }

                
            }

我遇到的问题是调用时未设置DocuSignEnvelopeInformation参数，因此代码始终终止于if == null语句。当我使用SoapUI将信封数据运行到API时，一切正常。我所缺少的任何想法将不胜感激。

编辑：我也想在这里添加接口，因为我最初忘记了它

    [ServiceContract(ConfigurationName = "IOperations", Namespace = "https://www.docusign.net/API/3.0")]
    public interface IOperations
    {
        
        [OperationContract(Action = "DocuSignConnectListener/Operations/DocuSignConnectUpdate")]
        [XmlSerializerFormat]
        string DocuSignConnectUpdate(DocuSignEnvelopeInformation DocuSignEnvelopeInformation);
    }