WCF parse data from stream

I have a service like following:

and when i post data from Postman with form-data in body like this:
" ------WebKitFormBoundarycTodfAxkLS0DHW9R Content-Disposition: form-data; name="username"

host ------WebKitFormBoundarycTodfAxkLS0DHW9R Content-Disposition: form-data; name="password"

P@ssword ------WebKitFormBoundarycTodfAxkLS0DHW9R-- ". I have a question. How to parse data to get username and password?

Somebody help me?

Thanks