Using Httpclient for send SOAP request In Asp.net Core - web-services

Question

Im using Asp.net Core, for calling an asmx service which has 4 methods and i want to call one of them by the name: Verify method, i do this steps:
1-Create realted SOAP:
private XmlDocument CreateSoapEnvelope(PayVM payModel)
{
XmlDocument soapEnvelop = new XmlDocument();
string requiredXML = string.Format(#"<SOAP-ENV:Envelope xmlns:SOAP-ENV=""http://schemas.xmlsoap.org/soap/envelope/"" xmlns:xsi=""http://www.w3.org/1999/XMLSchema-instance"" xmlns:xsd=""http://www.w3.org/1999/XMLSchema""><SOAP-ENV:Body><verifyTransaction xmlns=""http://tempuri.org/""> <String_1 xsi:type=""xsd:string"">{0}</String_1><String_2 xsi:type=""xsd:string"">{1}</String_2></verifyTransaction></SOAP-ENV:Body></SOAP-ENV:Envelope>", payModel.ReNO, payModel.MID);
soapEnvelop.LoadXml(requiredXML);
return soapEnvelop;
}
2-create the HttpClient and send my request:
XmlDocument soapRequest = CreateSoapEnvelope(iPGVerifyResultModel);
using (var client = new HttpClient())
{
var request = new HttpRequestMessage()
{
RequestUri = new Uri("relatedUri/ServiceName.asmx"),
Method = HttpMethod.Post
};
request.Content = new StringContent(soapRequest.ToString(), Encoding.UTF8, "text/xml");
request.Headers.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("text/xml"));
request.Content.Headers.ContentType = new MediaTypeHeaderValue("text/xml");
request.Headers.Add("SOAPAction", "Verify"); //I want to call this method
HttpResponseMessage response = client.SendAsync(request).Result;
if (!response.IsSuccessStatusCode)
{
throw new Exception();
}
Task<Stream> streamTask = response.Content.ReadAsStreamAsync();
Stream stream = streamTask.Result;
var sr = new StreamReader(stream);
var soapResponse = XDocument.Load(sr);
//do some other stuff...
}
but i didn't result, i try uses service by same parameters with Soap UI and the service work properly, but in my way i got StatusCode: 400 what is the problem?