Can not visit WebAPI about httplib

[j6mes]

Hi. Can you make a pull request for it please?

[wlfsky]

webapi code like this:
vs2017, iis10 on win10 64x, dotnet 4.6, mvc 5.2.3.0

class ValuesController : ApiController {
        [HttpPost]
        public async Task<Dictionary<string, string>> Post(int id = 0)
        {
            // if MultipartBodyProvider.cs string.Format("multipart/form-data, boundary={0}", boundary);
            // The following code will not pass 
            if (!Request.Content.IsMimeMultipartContent())
            {
                throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
            }
            Dictionary<string, string> dic = new Dictionary<string, string>();
            string root = HttpContext.Current.Server.MapPath("~/App_Data");
            var provider = new MultipartFormDataStreamProvider(root);
            try
            {
                // run to this code will be throw error "Unexpected end of MIME multipart stream. MIME multipart message is not complete"
                await Request.Content.ReadAsMultipartAsync(provider);

                foreach (MultipartFileData file in provider.FileData)
                {
                    Trace.WriteLine(file.Headers.ContentDisposition.FileName);
                    Trace.WriteLine("Server file path: "+file.LocalFileName);
                }
                foreach (var key in provider.FormData.AllKeys)
                {
                    dic.Add(key, provider.FormData[key]);
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
            return dic;
        }
}

the post code

Http.Post("http://localhost:90/api/values/1").Upload(files:
                new[] {
                        new NamedFileStream("zzz.zip", @"F:\zzz.zip", "application/octet-stream", File.OpenRead(@"F:\zzz.zip"))
            }).OnSuccess((s) =>
            {
                WriteLine("--success--");
                WriteLine(s);
            }).OnFail((s) =>
            {
                WriteLine("--fail--");
                WriteLine(s);
            }).Go();

normal form post will success

<form action="http://localhost:90/Api/Values/1" method="post" enctype="multipart/form-data">
    <input name="id" value="1" />
    <input id="d" type="file" src="F:\work\11.xls" name="d"/>
    <input id="e" type="file" src="F:\work\22.xls" name="e"/>
    <input type="submit" value="tj" />
</form>

thanks !