Web API and windows form

Question

User-941767363 posted

Hello,

I'm developing a windows form application (c#) that calls WEB API services (developed by me) and in particular I'm trying to "downloading" an Excel file (report) that it was previously created in a server folder ("Stampe").

I'm in trouble to "manage" client side, the response (HttpResponseMessage) from WEB API service.

• SERVER side:

   [HttpGet]
        public HttpResponseMessage GetFile(string FilePath, string FileName)
        {
            return GetFileStampa(FilePath, FileName);
        }

        public HttpResponseMessage GetFileStampa(string FilePath, string fileName)
        {
            var path = Path.Combine(FilePath, fileName);

            var response = new HttpResponseMessage(HttpStatusCode.OK);

            var stream = new FileStream(path, FileMode.Open);
            response.Content = new StreamContent(stream);

            response.Content.Headers.ContentType =
              new MediaTypeHeaderValue("application/octet-stream");
            response.Content.Headers.ContentDisposition =
              new ContentDispositionHeaderValue("attachment");
            response.Content.Headers.ContentDisposition.FileName = fileName;

            return response;
        }

• CLIENT side (windows form):

string FilePath = @"........\Stampe\";
            string FileName = @"Test.xlsx";

            string UrlGetFile = Url + "/File?" + "FilePath=" + FilePath + "&FileName=" + FileName;
            Uri UriGetFile = new Uri(UrlGetFile);
            HttpWebRequest request = WebRequest.Create(UriGetFile) as HttpWebRequest;
            request.Method = "GET";
            request.ContentType = "application/octet-stream"; //"text/xml";
            string results = string.Empty;
            HttpWebResponse response;
            using (response = request.GetResponse() as HttpWebResponse)
            {
                Stream objStream = response.GetResponseStream();
                BinaryReader breader = new BinaryReader(objStream);
                byte[] data = breader.ReadBytes((int)response.ContentLength);
                File.WriteAllBytes("d:\\temp\\MyTest.xlsx", data);
            }

the instruction "response.ContentLength" is always to -1. Message error: Non-negative number required

Where am I doing wrong (client or server side)?

Best

Stefano

Answer 1

User61956409 posted

Hi Stefano,

Message error: Non-negative number required

If the ContentLength is negative number, it will cause above issue. In your another thread, I shared the complete code snippet of Web API for clients consume to download file, and you said it seems also work for you.

[HttpGet]
public ActionResult GetFile(string FilePath, string FileName)
{
    return GetFileStampa(FilePath, FileName);
}

public ActionResult GetFileStampa(string FilePath, string fileName)
{
    var path = Path.Combine(FilePath, fileName);

    var response = new HttpResponseMessage(HttpStatusCode.OK);

    byte[] bytes = System.IO.File.ReadAllBytes(path);


    return File(bytes, "application/octet-stream");
}

With Regards,

Fei Han