using (System.Net.Http.HttpClient client = new System.Net.Http.HttpClient()) {

                client.BaseAddress = new Uri("http://192.168.1.3:42561");

                string api = "api/upload/uploadpost";

                MultipartFormDataContent content = new MultipartFormDataContent();

                string path1 = @"H:\图片\1.jpg";

                string path2 = @"H:\图片\2.jpg";

                FileStream fs1 = new FileStream(path1, FileMode.Open, FileAccess.Read);

                FileStream fs2 = new FileStream(path2, FileMode.Open, FileAccess.Read);

                content.Add(new StreamContent(fs1), "myFile1", Guid.NewGuid() + ".jpg");

                content.Add(new StreamContent(fs2), "myFile2", Guid.NewGuid() + ".jpg"); 

                //还可以添加键值对参数,web api 可以通过 request.Form["id"] 接收

                content.Add(new StringContent(""), "id");

                content.Add(new StringContent("wjire"), "name");

                content.Add(new StringContent(""), "age");

                var result = client.PostAsync(api, content).Result;

                var str = result.Content.ReadAsStringAsync().Result;

                fs1.Dispose();

                fs2.Dispose();

                Console.WriteLine(str);

            }

        public async Task<HttpResponseMessage> UploadPost() {

            var request = HttpContext.Current.Request;

            var id = request.Form["id"];

            var name = request.Form["name"];

            var age = request.Form["age"];

            var files = HttpContext.Current.Request.Files;

            var path = HttpContext.Current.Server.MapPath("/img/");

            if (files.Count > ) {

                foreach (string file in files) {

                    var img = files[file];

                    if (img?.ContentLength > ) {

                        var fileName = img.FileName;

                        await Task.Run(() => img.SaveAs(path + fileName));

                    }

                }

                return new HttpResponseMessage(HttpStatusCode.OK)

                {

                     Content = new StringContent("成功@!!!!!")

                };

            } else {

                var stream = request.InputStream;

                if (stream.Length > ) {

                    var bytes = new byte[stream.Length];

                    stream.Read(bytes, , bytes.Length);

                }

            }

            return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "没有文件");

        }