Not able to create SoapContext obj in web API

Aug 16 2018 8:16 AM
I am facing issue in web api, as i am creating web api service to client.
in this web api  iam using other services to create a request with attachement.
but SoapContext obj is not creating in my web api. 
using below line to create soapcontext obj 
SoapContext respContext = client.RequestSoapContext;
DimeAttachment dimeAttach = new DimeAttachment("image/gif", TypeFormat.MediaType, strpath);
 but evry time iam getting "respContext " as null.
Please help on this how can i create a obj to attach a file to the another service from my service.(i am using another service in my web api ) 

Brought to you by: