Not able to create SoapContext obj in web API

Question

Hi 

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);

respContext.Attachments.Add(dimeAttach);

 

 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 )