HOW-TO does "string Fetch(string fetchXml)" like (CRM 4 - CrmServiceWsdl) in CRM 2016?

    public partial class CrmService : System.Web.Services.Protocols.SoapHttpClientProtocol {

 [System.Web.Services.Protocols.SoapHeaderAttribute("CorrelationTokenValue")]
        [System.Web.Services.Protocols.SoapHeaderAttribute("CrmAuthenticationTokenValue")]
        [System.Web.Services.Protocols.SoapHeaderAttribute("CallerOriginTokenValue")]
        [System.Web.Services.Protocols.SoapDocumentMethodAttribute("http://schemas.microsoft.com/crm/2007/WebServices/Fetch", RequestNamespace="http://schemas.microsoft.com/crm/2007/WebServices", ResponseNamespace="http://schemas.microsoft.com/crm/2007/WebServices", Use=System.Web.Services.Description.SoapBindingUse.Literal, ParameterStyle=System.Web.Services.Protocols.SoapParameterStyle.Wrapped)]
        public string Fetch(string fetchXml) {
            object[] results = this.Invoke("Fetch", new object[] {
                        fetchXml});
            return ((string)(results[0]));
        }

  string result = aCrm.Fetch(fetchQuery);


                    if (result.ToString() == "<resultset morerecords=\"0\" />")
                    {
                        return "<codigoerror>01</codigoerror><descripcion>Mediador sin campañas</descripcion>";
                    }
                    else
                    {
                        XmlDocument xmlDoc = new XmlDocument();
                        xmlDoc.LoadXml(result);
                        XmlNodeList xmlNodes = xmlDoc.GetElementsByTagName("result");

                        for (int i = 0; i < xmlNodes.Count; i++)
                        {
                            string fetchquery2 = string.Empty;
                            fetchquery2 = ConsultasFetch.MostrarInfoCampaña();
                            fetchquery2 = fetchquery2.Replace("MiVariable1", MediadorCodeCPC);
                            fetchquery2 = fetchquery2.Replace("MiVariable2", xmlNodes.Item(i).FirstChild.FirstChild.Value.ToString());
                            string result2 = aCrm.Fetch(fetchquery2);

                            XmlDocument xmlDoc2 = new XmlDocument();
                            xmlDoc2.LoadXml(result2);
                            XmlNodeList xmlNodes2 = xmlDoc2.GetElementsByTagName("result");

                            for (int j = 0; j < xmlNodes2.Item(0).ChildNodes.Count; j++)

                            {
                                if (xmlNodes2.Item(0).ChildNodes.Item(j).Name == "new_informada")
                                {
                                    XmlElement xmlelem1 = xmlDoc.CreateElement("Informada");
                                    xmlelem1.InnerText = xmlNodes2.Item(0).ChildNodes[j].InnerXml;
                                    xmlDoc.ChildNodes.Item(0).ChildNodes.Item(i).AppendChild(xmlelem1);
                                }
                                else if (xmlNodes2.Item(0).ChildNodes.Item(j).Name == "new_fechainformada")
                                {
                                    XmlElement xmlelem2 = xmlDoc.CreateElement("Fecha");
                                    xmlelem2.InnerText = xmlNodes2.Item(0).ChildNodes[j].Attributes["date"].Value;
                                    xmlDoc.ChildNodes.Item(0).ChildNodes.Item(i).AppendChild(xmlelem2);

                                }
                                else if (xmlNodes2.Item(0).ChildNodes.Item(j).Name == "new_interescompromiso")
                                {
                                    XmlElement xmlelem3 = xmlDoc.CreateElement("Interes");
                                    xmlelem3.InnerText = xmlNodes2.Item(0).ChildNodes[j].InnerXml;
                                    xmlDoc.ChildNodes.Item(0).ChildNodes.Item(i).AppendChild(xmlelem3);
                                }

                            }


                        }