how to call web api to download document to website directory using webclient

Question

I am struggling with being able to create a file with its data based on the byte array returned from the WebAPI. The following is my code for making the call to the web api

 using (var http = new WebClient())
            {
                string url = string.Format("{0}api/FileUpload/FileServe?FileID=" + fileID, webApiUrl);
                http.Headers[HttpRequestHeader.ContentType] = "application/octet-stream";
                http.Headers[HttpRequestHeader.Authorization] = "Bearer " + authCookie.Value;
                http.DownloadDataCompleted += Http_DownloadDataCompleted;
                byte[] json = await http.DownloadDataTaskAsync(url);



            }

The api code is

[HttpGet]
    [Route("FileServe")]
    [Authorize(Roles = "Admin,SuperAdmin,Contractor")]
    public async Task<HttpResponseMessage> GetFile(int FileID)
    {
        using (var repo = new MBHDocRepository())
        {
            var file = await repo.GetSpecificFile(FileID);
            if (file == null)
            {
                throw new HttpResponseException(HttpStatusCode.BadRequest);
            }

            var stream = File.Open(file.PathLocator, FileMode.Open);
            HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
            response.Content = new StreamContent(stream);
            response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(file.FileType);
            return response;
        }
    }

I receive a byte array as a response however am unable to create the corresponding file from that byte array. I have no idea how to convert the byte array into the relevant file type (such as jpg, or pdf based on file type in the web api). any help will be appreciated.

Answer 1

Alright so there are a few ways of solving your problem firstly, on the server side of things you can either simply send the content type and leave it at that or you can also send the complete filename which helps you even further.

I have removed the code that is specific to your stuff with basic test code, please just ignore that stuff and use it in terms of your code.

Some design notes here:

            [HttpGet]
            [Route("FileServe")]
            [Authorize(Roles = "Admin,SuperAdmin,Contractor")]
            public async Task<HttpResponseMessage> GetFileAsync(int FileID) //<-- If your method returns Task have it be named with Async in it
            {
                using (var repo = new MBHDocRepository())
                {
                    var file = await repo.GetSpecificFile(FileID);
                    if (file == null)
                    {
                      throw new HttpResponseException(HttpStatusCode.BadRequest);
                    }

            var stream = File.Open(file.PathLocator, FileMode.Open);
            HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
            response.Content = new StreamContent(stream);
            response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(file.FileType);
            response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment") { FileName=Path.GetFileName(file.PathLocator)};
            return response;
                }
            }

Your client side code has two options here:

static void Main(string[] args)
        {
            using (var http = new WebClient())
            {


    string url = string.Format("{0}api/FileUpload/FileServe?FileID={1}",webApiUrl, fileId);
http.Headers[HttpRequestHeader.ContentType] = "application/octet-stream";
                http.Headers[HttpRequestHeader.Authorization] = "Bearer " + authCookie.Value;
                var response = http.OpenRead(url);
                var fs = new FileStream(String.Format(@"C:\Users\Bailey Miller\Downloads\{0}", GetName(http.ResponseHeaders)), FileMode.Create);
                response.CopyTo(fs); <-- how to move the stream to the actual file, this is not perfect and there are a lot of better examples

            fs.Flush();
            fs.Close();
            }


        }

        private static object GetName(WebHeaderCollection responseHeaders)
        {

            var c_type = responseHeaders.GetValues("Content-Type"); //<-- do a switch on this and return a really weird file name with the correct extension for the mime type.
        var cd = responseHeaders.GetValues("Content-Disposition")[0].Replace("\"", ""); <-- this gets the attachment type and filename param, also removes illegal character " from filename if present
        return cd.Substring(cd.IndexOf("=")+1); <-- extracts the file name
        }