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Using C# HttpClient to POST File without multipart/form-data

I'm trying to interact with a API that doesn't support multipart/form-data for uploading a file.
I've been able to get this to work with the older WebClient but since it's being deprecated I wanted to utilize the newer HttpClient.
The code I have for WebClient that works with this end point looks like this:
using (WebClient client = new WebClient())
{
byte[] file = File.ReadAllBytes(filePath);
client.Headers.Add("Authorization", apiKey);
client.Headers.Add("Content-Type", "application/pdf");
byte[] rawResponse = client.UploadData(uploadURI.ToString(), file);
string response = System.Text.Encoding.ASCII.GetString(rawResponse);
JsonDocument doc = JsonDocument.Parse(response);
return doc.RootElement.GetProperty("documentId").ToString();
}
I've not found a way to get an equivalent upload to work with HttpClient since it seems to always use multipart.

I think it would look something like this
using var client = new HttpClient();
var file = File.ReadAllBytes(filePath);
var content = new ByteArrayContent(file);
content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
var result = await client.PostAsync(uploadURI.ToString(), content);
result.EnsureSuccessStatusCode();
var response = await result.Content.ReadAsStringAsync();
var doc = JsonDocument.Parse(response);
return doc.RootElement.GetProperty("documentId").ToString();

What speaks against using simply HttpClient's PostAsync method in conjunction with ByteArrayContent?
byte[] fileData = ...;
var payload = new ByteArrayContent(fileData);
payload.Headers.Add("Content-Type", "application/pdf");
myHttpClient.PostAsync(uploadURI, payload);

Response Content-Length mismatch: too few bytes written

My ASP.NET Core app uses "out-of-box" external login authentication. What I want to implement - on facebook challenge I want to wrap redirect url and return it as json to consume in jquery frontend. But after request ends I see 500 error in browser and next error in application console:
fail: Microsoft.AspNetCore.Server.Kestrel[13]
Connection id "0HLV651D6KVJC", Request id "0HLV651D6KVJC:00000005": An unhandled exception was thrown by the
application. System.InvalidOperationException: Response Content-Length
mismatch: too few bytes written (0 of 470).
My external login action, nothing special to look at
[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public IActionResult ExternalLogin(string provider, string returnUrl = null)
{
// Request a redirect to the external login provider.
var redirectUrl = Url.Action(nameof(ExternalLoginCallback), "Account", new { returnUrl });
var properties = _signInManager.ConfigureExternalAuthenticationProperties(provider, redirectUrl);
return Challenge(properties, provider);
}
Facebook authentication configuration:
services.AddAuthentication().AddFacebook(facebookOptions =>
{
facebookOptions.AppId = Configuration["Authentication:Facebook:AppId"];
facebookOptions.AppSecret = Configuration["Authentication:Facebook:AppSecret"];
facebookOptions.Events.OnRedirectToAuthorizationEndpoint =
async (x) =>
{
UTF8Encoding encoding = new UTF8Encoding();
var content = JsonConvert.SerializeObject(new { redirect_url = x.RedirectUri });
byte[] bytes = encoding.GetBytes(content);
x.Response.StatusCode = 200;
x.Response.ContentLength = bytes.Length;
x.Response.ContentType = "text/plain";
x.Response.Body = new MemoryStream();
await x.Response.WriteAsync(content);
// at this point I see that x.Response.Body.Length == 470, but message states there are 0 of 470 written
};
});
Is there any way I could make it work?

This can also happen when using new C# using syntax like this:
using var ms = new MemoryStream();
using var writer = new StreamWriter(ms);
writer.WriteLine("my content");
memoryStream.Position = 0;
return File(ms, "text/plain");
in this case, the MemoryStream is accessed before the StreamWriter is flushed. Either use old syntax for the StreamWriter:
using var ms = new MemoryStream();
using (var writer = new StreamWriter(ms, Encoding.UTF8, -1, true))
{
writer.WriteLine("my content");
}
memoryStream.Position = 0;
return File(ms, "text/plain");
or flush the writer:
using var ms = new MemoryStream();
using var writer = new StreamWriter(ms);
writer.WriteLine("my content");
writer.Flush();
memoryStream.Position = 0;
return File(ms, "text/plain");

Changed code to write to original response stream and it works now.
facebookOptions.Events.OnRedirectToAuthorizationEndpoint =
async (x) =>
{
var content = JsonConvert.SerializeObject(new { redirect_url = x.RedirectUri });
x.Response.StatusCode = 200;
x.Response.ContentType = "text/plain";
await x.Response.WriteAsync(content);
};

You can use something like this:
var stream = new MemoryStream();
/// writing to the stream
if (stream.CanSeek)
{
stream.Seek(0, SeekOrigin.Begin);
}
/// then read stream

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

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.

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
}

How to post and receive a file with web api

I have a Api Post method that I want to be able to accept any file type and that looks like this:
[HttpPost]
public async Task<IHttpActionResult> Post()
{
if (!Request.Content.IsMimeMultipartContent())
{
throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
}
var provider = new MultipartMemoryStreamProvider();
await Request.Content.ReadAsMultipartAsync(provider);
if (provider.Contents.Count != 1)
{
throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.BadRequest,
"You must include exactly one file per request."));
}
var file = provider.Contents[0];
var filename = file.Headers.ContentDisposition.FileName.Trim('\"');
var buffer = await file.ReadAsByteArrayAsync();
}
This works in fiddler when I try to post an image to it. However, I'm writing a client library and I have a method that looks like this:
public string PostAttachment(byte[] data, Uri endpoint, string contentType)
{
var request = (HttpWebRequest)WebRequest.Create(endpoint);
request.Method = "POST";
request.ContentType = contentType;
request.ContentLength = data.Length;
var stream = request.GetRequestStream();
stream.Write(data, 0, data.Length);
stream.Close();
var response = (HttpWebResponse) request.GetResponse();
using (var reader = new StreamReader(response.GetResponseStream()))
{
return reader.ReadToEnd();
}
}
Whenever I try to post an image using this, I'm getting a UnsuportedMediaType error. I'm assuming it's because my image isn't Multi Part Content? Is there an easy way to make my request of the correct type?
If I have to change my web api post method, is there an easy way of doing that without writing files to the server and keeping it in memory?

The MultipartFormDataContent from the System.Net.Http namespace will allow you to post multipart form data.
private async Task<string> PostAttachment(byte[] data, Uri url, string contentType)
{
HttpContent content = new ByteArrayContent(data);
content.Headers.ContentType = new MediaTypeHeaderValue(contentType);
using (var form = new MultipartFormDataContent())
{
form.Add(content);
using(var client = new HttpClient())
{
var response = await client.PostAsync(url, form);
return await response.Content.ReadAsStringAsync();
}
}
}

Using Catchoom in C# WP8.1 project

i want to use catchoom in c# , but not able to find any sample could any one please provide any sample code if have.
i have got this sample of curl
curl -F "image=#CATask1-Correct.png" -F "token=sometoken" https://r.catchoom.com/v1/search
Can some one covert this to c# ?
I tried to convert it as shown below:
Here's my code:
public static async Task<string> Upload(byte[] image)
{
using (var client = new HttpClient())
{
// string boundary = "---XXX---";
using (var content = new MultipartFormDataContent())
{
string token = "sometoken";
MemoryStream stream = new MemoryStream();
StreamWriter writer = new StreamWriter(stream);
writer.Write(token);
writer.Flush();
stream.Position = 0;
// adding Token and Image to the request
content.Add(new StreamContent(stream), "token");
content.Add(new StreamContent(new MemoryStream(image)), "bilddatei", "upload.jpg");
using (
var message = await client.PostAsync("https://r.catchoom.com/v1/search", content))
{
var input = await message.Content.ReadAsStringAsync();
return input;
}
}
}
}
then I called the method in the on-click event handler:
private async void mybtn_Click(object sender, RoutedEventArgs e)
{
// converting the image to a byte array
BitmapImage bitmapImage = new BitmapImage(new Uri("http://www.familyfuntwincities.com/wp-content/uploads/2013/09/apple_red_1_clipart.png?s=128&g=1"));
RandomAccessStreamReference rasr = RandomAccessStreamReference.CreateFromUri(bitmapImage.UriSource);
var streamWithContent = await rasr.OpenReadAsync();
byte[] buffer = new byte[streamWithContent.Size];
await streamWithContent.ReadAsync(buffer.AsBuffer(), (uint)streamWithContent.Size, InputStreamOptions.None);
// calling the upload method
string output = await Upload(buffer);
mytext1.Text = output;
}
but I keep getting "image is missing" error from the catchoom server although I managed to upload the image to other servers in the same way ( without the token part of course).
My question is: How to add multipule part content? what's the right boundary between the Token part and the image part in order to be recognized by catchoom?

Here is what worked for me:
public static async Task<string> Test(string token, Stream stream, string fileName)
{
HttpClient client = new HttpClient();
MultipartFormDataContent content = new MultipartFormDataContent();
content.Add(new StringContent(token), "token");
content.Add(new StreamContent(stream), "image", fileName);
var resp = await client.PostAsync("https://r.catchoom.com/v1/search", content);
return await resp.Content.ReadAsStringAsync();
}
If you wanted to use the image you listed in your sample, here is how I would fetch it:
HttpClient client = new HttpClient();
var stream = await client.GetStreamAsync("http://www.familyfuntwincities.com/wp-content/uploads/2013/09/apple_red_1_clipart.png?s=128&g=1");
return await Test("<SOME_TOKEN_VALUE>", stream, "apple.png");
However the API claims that the image is unsupported due to alpha transparency. You can find some other samples that show you how to strip alpha transparency if that is important. The above code worked fine for images that don't have alpha transparency.