c# - Windows Phone 8.1 MultipartFormDataContent is missing -

why can't use multipartformdatacontent , streamcontent?
getting following error:

the type or namespace name 'multipartformdatacontent' not found (are missing using directive or assembly reference?)

here code:

var fileuploadurl = @"http://<ipaddress>:<port>/fileupload";                 var client = new httpclient();                 photostream.position = 0;                 multipartformdatacontent content = new multipartformdatacontent();                 content.add(new streamcontent(photostream), "file", filename);                 await client.postasync(fileuploadurl, content)                     .continuewith((posttask) =>                     {                         posttask.result.ensuresuccessstatuscode();                     }); 

you have add system.net.http class

using system.net.http