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How to write Testcases for an API that accepts an object that includes IFormFile typed fields in .NET

This is my controller code. Here it accepts UpdateMediaDto object that contains IFormFile data ( e.g. images and audios).
[HttpPut("words/{wordId}/medias/{id}")]
public async Task<ActionResult<WordMediaDto>> UpdateWordMedia(Guid wordId, Guid id, [FromForm] UpdateMediaDto mediaDto)
{
WordMedia? media = await _unitOfWork.WordMediaRepository.GetByIdAsync(id);
if (media == null) return NotFound();
if (wordId != media.WordId) return BadRequest("No Word present for this media");
var newMedia = _mediaFileMasterService.UpdateMedias(mediaDto);
//............
}
And this is my testcase
[Fact]
public async Task PUT_Media_with_UpdateMediaDto_results_WordMediaDto_success()
{
var ImagefileMock = new Mock<IFormFile>();
var content = System.Text.Encoding.UTF8.GetBytes("// byte[]....");
var ImagefileName = "sampleImage.jpg";
var ms = new MemoryStream();
var writer = new StreamWriter(ms);
writer.Write(content);
writer.Flush();
ms.Position = 0;
ImagefileMock.Setup(_ => _.OpenReadStream()).Returns(ms);
ImagefileMock.Setup(_ => _.FileName).Returns(ImagefileName);
ImagefileMock.Setup(_ => _.Length).Returns(ms.Length);
UpdateMediaDto mediaDto = new() {
Id = Guid.Parse("f1659b04-85a3-4969-7d20-08da081a9616"),
wordId=Guid.Parse("2caf24aa-4d37-4f64-aa91-4a605798c35b"),
PrimaryImage=ImagefileMock.Object,
SecondaryImage1 = ImagefileMock.Object };
HttpContent httpContent = new StringContent(JsonConvert.SerializeObject(mediaDto), Encoding.UTF8);
httpContent.Headers.ContentType = new MediaTypeHeaderValue("multipart/form-data");
//Act
var response = await _httpClient.PutAsync("api/v1/admin/words/d9823bdd-0d11-42e5-a804-4d59d393d2bc/medias/f47136e3-754a-4f2b-b5cc-08da2d91a92e", httpContent);
//Assert
response.EnsureSuccessStatusCode();
}
But Here I can't serialize the object using SerializeObject. when I execute this test case I get an error like
Newtonsoft.Json.JsonSerializationException : Self referencing loop detected for property 'Object' with type 'Castle.Proxies.IFormFileProxy'. Path 'PrimaryImage.Mock'.
How can I solve this problem... and is there any other ways to test API like this?

The proxy created by MOQ is causing an issue with the serialization in this case.
Consider using an actual FormFile instance which is derived from IFormFile.
[Fact]
public async Task PUT_Media_with_UpdateMediaDto_results_WordMediaDto_success() {
//Setup mock file using a memory stream
string content = System.Text.Encoding.UTF8.GetBytes("// byte[]....");
string ImagefileName = "sampleImage.jpg";
MemoryStream ms = new MemoryStream();
StreamWriter writer = new StreamWriter(ms);
writer.Write(content);
writer.Flush();
ms.Position = 0;
//create FormFile with desired data
IFormFile ImagefileMock = new FormFile(ms, 0, ms.Length, "name_from_form", ImagefileName);
UpdateMediaDto mediaDto = new() {
Id = Guid.Parse("f1659b04-85a3-4969-7d20-08da081a9616"),
wordId=Guid.Parse("2caf24aa-4d37-4f64-aa91-4a605798c35b"),
PrimaryImage=ImagefileMock,
SecondaryImage1 = ImagefileMock
};
HttpContent httpContent = new StringContent(JsonConvert.SerializeObject(mediaDto), Encoding.UTF8);
httpContent.Headers.ContentType = new MediaTypeHeaderValue("multipart/form-data");
//Act
var response = await _httpClient.PutAsync("api/v1/admin/words/d9823bdd-0d11-42e5-a804-4d59d393d2bc/medias/f47136e3-754a-4f2b-b5cc-08da2d91a92e", httpContent);
//Assert
response.EnsureSuccessStatusCode();
}

It seems you need to use MultipartFormDataContent to build your form and add parts. To Stream objects use StreamContent.
var multiPartformData = new MultipartFormDataContent();
var streamContent = new StreamContent(ImagefileMock);
multiPartformData .Add(streamContent);

How to implement WebClient.UploadFileAsync with HttpClient? [duplicate]

Does anyone know how to use the HttpClient in .Net 4.5 with multipart/form-data upload?
I couldn't find any examples on the internet.

my result looks like this:
public static async Task<string> Upload(byte[] image)
{
using (var client = new HttpClient())
{
using (var content =
new MultipartFormDataContent("Upload----" + DateTime.Now.ToString(CultureInfo.InvariantCulture)))
{
content.Add(new StreamContent(new MemoryStream(image)), "bilddatei", "upload.jpg");
using (
var message =
await client.PostAsync("http://www.directupload.net/index.php?mode=upload", content))
{
var input = await message.Content.ReadAsStringAsync();
return !string.IsNullOrWhiteSpace(input) ? Regex.Match(input, #"http://\w*\.directupload\.net/images/\d*/\w*\.[a-z]{3}").Value : null;
}
}
}
}

It works more or less like this (example using an image/jpg file):
async public Task<HttpResponseMessage> UploadImage(string url, byte[] ImageData)
{
var requestContent = new MultipartFormDataContent();
// here you can specify boundary if you need---^
var imageContent = new ByteArrayContent(ImageData);
imageContent.Headers.ContentType =
MediaTypeHeaderValue.Parse("image/jpeg");
requestContent.Add(imageContent, "image", "image.jpg");
return await client.PostAsync(url, requestContent);
}
(You can requestContent.Add() whatever you want, take a look at the HttpContent descendant to see available types to pass in)
When completed, you'll find the response content inside HttpResponseMessage.Content that you can consume with HttpContent.ReadAs*Async.

This is an example of how to post string and file stream with HTTPClient using MultipartFormDataContent. The Content-Disposition and Content-Type need to be specified for each HTTPContent:
Here's my example. Hope it helps:
private static void Upload()
{
using (var client = new HttpClient())
{
client.DefaultRequestHeaders.Add("User-Agent", "CBS Brightcove API Service");
using (var content = new MultipartFormDataContent())
{
var path = #"C:\B2BAssetRoot\files\596086\596086.1.mp4";
string assetName = Path.GetFileName(path);
var request = new HTTPBrightCoveRequest()
{
Method = "create_video",
Parameters = new Params()
{
CreateMultipleRenditions = "true",
EncodeTo = EncodeTo.Mp4.ToString().ToUpper(),
Token = "x8sLalfXacgn-4CzhTBm7uaCxVAPjvKqTf1oXpwLVYYoCkejZUsYtg..",
Video = new Video()
{
Name = assetName,
ReferenceId = Guid.NewGuid().ToString(),
ShortDescription = assetName
}
}
};
//Content-Disposition: form-data; name="json"
var stringContent = new StringContent(JsonConvert.SerializeObject(request));
stringContent.Headers.Add("Content-Disposition", "form-data; name=\"json\"");
content.Add(stringContent, "json");
FileStream fs = File.OpenRead(path);
var streamContent = new StreamContent(fs);
streamContent.Headers.Add("Content-Type", "application/octet-stream");
//Content-Disposition: form-data; name="file"; filename="C:\B2BAssetRoot\files\596090\596090.1.mp4";
streamContent.Headers.Add("Content-Disposition", "form-data; name=\"file\"; filename=\"" + Path.GetFileName(path) + "\"");
content.Add(streamContent, "file", Path.GetFileName(path));
//content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
Task<HttpResponseMessage> message = client.PostAsync("http://api.brightcove.com/services/post", content);
var input = message.Result.Content.ReadAsStringAsync();
Console.WriteLine(input.Result);
Console.Read();
}
}
}

Try this its working for me.
private static async Task<object> Upload(string actionUrl)
{
Image newImage = Image.FromFile(#"Absolute Path of image");
ImageConverter _imageConverter = new ImageConverter();
byte[] paramFileStream= (byte[])_imageConverter.ConvertTo(newImage, typeof(byte[]));
var formContent = new MultipartFormDataContent
{
// Send form text values here
{new StringContent("value1"),"key1"},
{new StringContent("value2"),"key2" },
// Send Image Here
{new StreamContent(new MemoryStream(paramFileStream)),"imagekey","filename.jpg"}
};
var myHttpClient = new HttpClient();
var response = await myHttpClient.PostAsync(actionUrl.ToString(), formContent);
string stringContent = await response.Content.ReadAsStringAsync();
return response;
}

Here is another example on how to use HttpClient to upload a multipart/form-data.
It uploads a file to a REST API and includes the file itself (e.g. a JPG) and additional API parameters. The file is directly uploaded from local disk via FileStream.
See here for the full example including additional API specific logic.
public static async Task UploadFileAsync(string token, string path, string channels)
{
// we need to send a request with multipart/form-data
var multiForm = new MultipartFormDataContent();
// add API method parameters
multiForm.Add(new StringContent(token), "token");
multiForm.Add(new StringContent(channels), "channels");
// add file and directly upload it
FileStream fs = File.OpenRead(path);
multiForm.Add(new StreamContent(fs), "file", Path.GetFileName(path));
// send request to API
var url = "https://slack.com/api/files.upload";
var response = await client.PostAsync(url, multiForm);
}

Here's a complete sample that worked for me. The boundary value in the request is added automatically by .NET.
var url = "http://localhost/api/v1/yourendpointhere";
var filePath = #"C:\path\to\image.jpg";
HttpClient httpClient = new HttpClient();
MultipartFormDataContent form = new MultipartFormDataContent();
FileStream fs = File.OpenRead(filePath);
var streamContent = new StreamContent(fs);
var imageContent = new ByteArrayContent(streamContent.ReadAsByteArrayAsync().Result);
imageContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data");
form.Add(imageContent, "image", Path.GetFileName(filePath));
var response = httpClient.PostAsync(url, form).Result;

Example with preloader Dotnet 3.0 Core
ProgressMessageHandler processMessageHander = new ProgressMessageHandler();
processMessageHander.HttpSendProgress += (s, e) =>
{
if (e.ProgressPercentage > 0)
{
ProgressPercentage = e.ProgressPercentage;
TotalBytes = e.TotalBytes;
progressAction?.Invoke(progressFile);
}
};
using (var client = HttpClientFactory.Create(processMessageHander))
{
var uri = new Uri(transfer.BackEndUrl);
client.DefaultRequestHeaders.Authorization =
new AuthenticationHeaderValue("Bearer", AccessToken);
using (MultipartFormDataContent multiForm = new MultipartFormDataContent())
{
multiForm.Add(new StringContent(FileId), "FileId");
multiForm.Add(new StringContent(FileName), "FileName");
string hash = "";
using (MD5 md5Hash = MD5.Create())
{
var sb = new StringBuilder();
foreach (var data in md5Hash.ComputeHash(File.ReadAllBytes(FullName)))
{
sb.Append(data.ToString("x2"));
}
hash = result.ToString();
}
multiForm.Add(new StringContent(hash), "Hash");
using (FileStream fs = File.OpenRead(FullName))
{
multiForm.Add(new StreamContent(fs), "file", Path.GetFileName(FullName));
var response = await client.PostAsync(uri, multiForm);
progressFile.Message = response.ToString();
if (response.IsSuccessStatusCode) {
progressAction?.Invoke(progressFile);
} else {
progressErrorAction?.Invoke(progressFile);
}
response.EnsureSuccessStatusCode();
}
}
}

I'm adding a code snippet which shows on how to post a file to an API which has been exposed over DELETE http verb. This is not a common case to upload a file with DELETE http verb but it is allowed. I've assumed Windows NTLM authentication for authorizing the call.
The problem that one might face is that all the overloads of HttpClient.DeleteAsync method have no parameters for HttpContent the way we get it in PostAsync method
var requestUri = new Uri("http://UrlOfTheApi");
using (var streamToPost = new MemoryStream("C:\temp.txt"))
using (var fileStreamContent = new StreamContent(streamToPost))
using (var httpClientHandler = new HttpClientHandler() { UseDefaultCredentials = true })
using (var httpClient = new HttpClient(httpClientHandler, true))
using (var requestMessage = new HttpRequestMessage(HttpMethod.Delete, requestUri))
using (var formDataContent = new MultipartFormDataContent())
{
formDataContent.Add(fileStreamContent, "myFile", "temp.txt");
requestMessage.Content = formDataContent;
var response = httpClient.SendAsync(requestMessage).GetAwaiter().GetResult();
if (response.IsSuccessStatusCode)
{
// File upload was successfull
}
else
{
var erroResult = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
throw new Exception("Error on the server : " + erroResult);
}
}
You need below namespaces at the top of your C# file:
using System;
using System.Net;
using System.IO;
using System.Net.Http;
P.S. You are seeing a number of using blocks(IDisposable pattern) in the above code snippet which doesn't look very clean. Unfortunately, the syntax of using construct doesn't support initializing multiple variables in single statement.

X509Certificate clientKey1 = null;
clientKey1 = new X509Certificate(AppSetting["certificatePath"],
AppSetting["pswd"]);
string url = "https://EndPointAddress";
FileStream fs = File.OpenRead(FilePath);
var streamContent = new StreamContent(fs);
var FileContent = new ByteArrayContent(streamContent.ReadAsByteArrayAsync().Result);
FileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("ContentType");
var handler = new WebRequestHandler();
handler.ClientCertificateOptions = ClientCertificateOption.Manual;
handler.ClientCertificates.Add(clientKey1);
handler.ServerCertificateValidationCallback = (httpRequestMessage, cert, cetChain, policyErrors) =>
{
return true;
};
using (var client = new HttpClient(handler))
{
// Post it
HttpResponseMessage httpResponseMessage = client.PostAsync(url, FileContent).Result;
if (!httpResponseMessage.IsSuccessStatusCode)
{
string ss = httpResponseMessage.StatusCode.ToString();
}
}

public async Task<object> PassImageWithText(IFormFile files)
{
byte[] data;
string result = "";
ByteArrayContent bytes;
MultipartFormDataContent multiForm = new MultipartFormDataContent();
try
{
using (var client = new HttpClient())
{
using (var br = new BinaryReader(files.OpenReadStream()))
{
data = br.ReadBytes((int)files.OpenReadStream().Length);
}
bytes = new ByteArrayContent(data);
multiForm.Add(bytes, "files", files.FileName);
multiForm.Add(new StringContent("value1"), "key1");
multiForm.Add(new StringContent("value2"), "key2");
var res = await client.PostAsync(_MEDIA_ADD_IMG_URL, multiForm);
}
}
catch (Exception e)
{
throw new Exception(e.ToString());
}
return result;
}

How to post form-data IFormFile with HttpClient?

I have backend endpoint Task<ActionResult> Post(IFormFile csvFile) and I need to call this endpoint from HttpClient. Currently I am getting Unsupported media type error.
Here is my code:
var filePath = Path.Combine("IntegrationTests", "file.csv");
var gg = File.ReadAllBytes(filePath);
var byteArrayContent = new ByteArrayContent(gg);
var postResponse = await _client.PostAsync("offers", new MultipartFormDataContent
{
{byteArrayContent }
});

You need to specify parameter name in MultipartFormDataContent collection matching action parameter name (csvFile) and a random file name
var multipartContent = new MultipartFormDataContent();
multipartContent.Add(byteArrayContent, "csvFile", "filename");
var postResponse = await _client.PostAsync("offers", multipartContent);
or equivalent
var postResponse = await _client.PostAsync("offers", new MultipartFormDataContent {
{ byteArrayContent, "csvFile", "filename" }
});

Use this snippet:
const string url = "https://localhost:5001/api/Upload";
const string filePath = #"C:\Path\To\File.png";
using (var httpClient = new HttpClient())
{
using (var form = new MultipartFormDataContent())
{
using (var fs = File.OpenRead(filePath))
{
using (var streamContent = new StreamContent(fs))
{
using (var fileContent = new ByteArrayContent(await streamContent.ReadAsByteArrayAsync()))
{
fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data");
// "file" parameter name should be the same as the server side input parameter name
form.Add(fileContent, "file", Path.GetFileName(filePath));
HttpResponseMessage response = await httpClient.PostAsync(url, form);
}
}
}
}
}

This worked for me as a generic
public static Task<HttpResponseMessage> PostFormDataAsync<T>(this HttpClient httpClient, string url, string token, T data)
{
var content = new MultipartFormDataContent();
foreach (var prop in data.GetType().GetProperties())
{
var value = prop.GetValue(data);
if (value is FormFile)
{
var file = value as FormFile;
content.Add(new StreamContent(file.OpenReadStream()), prop.Name, file.FileName);
content.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data") { Name = prop.Name, FileName = file.FileName };
}
else
{
content.Add(new StringContent(JsonConvert.SerializeObject(value)), prop.Name);
}
}
if (!string.IsNullOrWhiteSpace(token))
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
return httpClient.PostAsync(url, content);
}

Solved by using this code:
const string fileName = "csvFile.csv";
var filePath = Path.Combine("IntegrationTests", fileName);
var bytes = File.ReadAllBytes(filePath);
var form = new MultipartFormDataContent();
var content = new StreamContent(new MemoryStream(bytes));
form.Add(content, "csvFile");
content.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data")
{
Name = "csvFile",
FileName = fileName
};
content.Headers.Remove("Content-Type");
content.Headers.Add("Content-Type", "application/octet-stream; boundary=----WebKitFormBoundaryMRxYYlVt8KWT8TU3");
form.Add(content);
//Act
var postResponse = await _sellerClient.PostAsync("items/upload", form);

Post the attachment as an MultipartFormDataContent
var type = typeof(Startup);
var stream = type.Assembly.GetManifestResourceStream(type, "Resources.New.docx");
var fileContent = new StreamContent(stream);
var data = new MultipartFormDataContent
{
{ fileContent, "file", "New.docx" }
};
var response = await _client.PostAsync("upload", multipartContent);
Source: https://medium.com/#woeterman_94/c-webapi-upload-files-to-a-controller-e5ccf288b0ca

Please see the following working code with .NET 5.0 Environment.
You send the file as a byte[] and receive it as a IFormFile in the API.
//api controller receiver
[HttpPost("SendBackupFiles")]
public IActionResult SendBackupFiles(IFormFile file)
{
var filePath = Path.GetTempFileName();
using (var stream = System.IO.File.Create(filePath))
file.CopyToAsync(stream);
}
//client code sender example, not optimized lol.
const string filePath = #"C:\temp\hallo.csv";
using (var httpClient = new HttpClient())
{
var form = new MultipartFormDataContent();
byte[] fileData = File.ReadAllBytes(filePath);
ByteArrayContent byteContent = new ByteArrayContent(fileData);
byteContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data");
form.Add(byteContent, "file", Path.GetFileName(filePath));
var result = httpClient.PostAsync("http://localhost:5070/..yourControllerName.../SendBackupFiles", form).ConfigureAwait(false).GetAwaiter().GetResult().Content.ReadAsStringAsync().Result;
}

How to return a file (FileContentResult) in ASP.NET WebAPI

In a regular MVC controller, we can output pdf with a FileContentResult.
public FileContentResult Test(TestViewModel vm)
{
var stream = new MemoryStream();
//... add content to the stream.
return File(stream.GetBuffer(), "application/pdf", "test.pdf");
}
But how can we change it into an ApiController?
[HttpPost]
public IHttpActionResult Test(TestViewModel vm)
{
//...
return Ok(pdfOutput);
}
Here is what I've tried but it doesn't seem to work.
[HttpGet]
public IHttpActionResult Test()
{
var stream = new MemoryStream();
//...
var content = new StreamContent(stream);
content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
content.Headers.ContentLength = stream.GetBuffer().Length;
return Ok(content);
}
The returned result displayed in the browser is:
{"Headers":[{"Key":"Content-Type","Value":["application/pdf"]},{"Key":"Content-Length","Value":["152844"]}]}
And there is a similar post on SO: Returning binary file from controller in ASP.NET Web API
. It talks about output an existing file. But I could not make it work with a stream.
Any suggestions?

Instead of returning StreamContent as the Content, I can make it work with ByteArrayContent.
[HttpGet]
public HttpResponseMessage Generate()
{
var stream = new MemoryStream();
// processing the stream.
var result = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new ByteArrayContent(stream.ToArray())
};
result.Content.Headers.ContentDisposition =
new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
{
FileName = "CertificationCard.pdf"
};
result.Content.Headers.ContentType =
new MediaTypeHeaderValue("application/octet-stream");
return result;
}

If you want to return IHttpActionResult you can do it like this:
[HttpGet]
public IHttpActionResult Test()
{
var stream = new MemoryStream();
var result = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new ByteArrayContent(stream.GetBuffer())
};
result.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
{
FileName = "test.pdf"
};
result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
var response = ResponseMessage(result);
return response;
}

This question helped me.
So, try this:
Controller code:
[HttpGet]
public HttpResponseMessage Test()
{
var path = System.Web.HttpContext.Current.Server.MapPath("~/Content/test.docx");;
HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
var stream = new FileStream(path, FileMode.Open);
result.Content = new StreamContent(stream);
result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
result.Content.Headers.ContentDisposition.FileName = Path.GetFileName(path);
result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
result.Content.Headers.ContentLength = stream.Length;
return result;
}
View Html markup (with click event and simple url):
<script type="text/javascript">
$(document).ready(function () {
$("#btn").click(function () {
// httproute = "" - using this to construct proper web api links.
window.location.href = "#Url.Action("GetFile", "Data", new { httproute = "" })";
});
});
</script>
<button id="btn">
Button text
</button>
Data

Here is an implementation that streams the file's content out without buffering it (buffering in byte[] / MemoryStream, etc. can be a server problem if it's a big file).
public class FileResult : IHttpActionResult
{
public FileResult(string filePath)
{
if (filePath == null)
throw new ArgumentNullException(nameof(filePath));
FilePath = filePath;
}
public string FilePath { get; }
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
var response = new HttpResponseMessage(HttpStatusCode.OK);
response.Content = new StreamContent(File.OpenRead(FilePath));
var contentType = MimeMapping.GetMimeMapping(Path.GetExtension(FilePath));
response.Content.Headers.ContentType = new MediaTypeHeaderValue(contentType);
return Task.FromResult(response);
}
}
It can be simply used like this:
public class MyController : ApiController
{
public IHttpActionResult Get()
{
string filePath = GetSomeValidFilePath();
return new FileResult(filePath);
}
}

I am not exactly sure which part to blame, but here's why MemoryStream doesn't work for you:
As you write to MemoryStream, it increments its Position property.
The constructor of StreamContent takes into account the stream's current Position. So if you write to the stream, then pass it to StreamContent, the response will start from the nothingness at the end of the stream.
There's two ways to properly fix this:
construct content, write to stream
[HttpGet]
public HttpResponseMessage Test()
{
var stream = new MemoryStream();
var response = Request.CreateResponse(HttpStatusCode.OK);
response.Content = new StreamContent(stream);
// ...
// stream.Write(...);
// ...
return response;
}
write to stream, reset position, construct content
[HttpGet]
public HttpResponseMessage Test()
{
var stream = new MemoryStream();
// ...
// stream.Write(...);
// ...
stream.Position = 0;
var response = Request.CreateResponse(HttpStatusCode.OK);
response.Content = new StreamContent(stream);
return response;
}
looks a little better if you have a fresh Stream, 1) is simpler if your stream does not start at 0

For me it was the difference between
var response = Request.CreateResponse(HttpStatusCode.OK, new StringContent(log, System.Text.Encoding.UTF8, "application/octet-stream");
and
var response = Request.CreateResponse(HttpStatusCode.OK);
response.Content = new StringContent(log, System.Text.Encoding.UTF8, "application/octet-stream");
The first one was returning the JSON representation of StringContent: {"Headers":[{"Key":"Content-Type","Value":["application/octet-stream; charset=utf-8"]}]}
While the second one was returning the file proper.
It seems that Request.CreateResponse has an overload that takes a string as the second parameter and this seems to have been what was causing the StringContent object itself to be rendered as a string, instead of the actual content.

I found this article useful: https://codeburst.io/download-files-using-web-api-ae1d1025f0a9
Basically it says:
[Route("api/[controller]")]
[ApiController]
public class JobController : ControllerBase
{
[HttpGet]
public ActionResult GetFile()
{
byte[] fileContent = GetFile();
return File(fileContent, "application/pdf", "test.pdf");
}
}

var memoryStream = new MemoryStream();
await cloudFile.DownloadToStreamAsync(memoryStream);
responseMessage.result = "Success";
var contentType = "application/octet-stream";
**using (var stream = new MemoryStream())
{
return File(memoryStream.GetBuffer(), contentType, "Cartage.pdf");
}**

HttpClient Post photo WITH message to Facebook Graph

Issue
I am trying to upload a photo to the Facebook API WITH a message.
Code Snippet - Upload
requestUri = "https://graph.facebook.com/v2.0/me/photos?access_token=MyAccessToken"
var streamContent = new StreamContent(fileStream);
streamContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data")
{
Name = "\"files\"",
FileName = "\"image.jpg\""
};
streamContent.Headers.ContentType = new MediaTypeHeaderValue("image/jpeg");
var messageContent = new StringContent("message=HelloWorld");
var resultJson = webRequestClient.Post(requestUri, new MultipartFormDataContent()
{
messageContent,
streamContent,
});
Code - webRequestClient
public string Post(string uri, HttpContent postData)
{
return PostAsync(uri, postData).Result;
}
public async Task<string> PostAsync(string uri, HttpContent httpContent)
{
string resultStream;
using (var httpClient = new HttpClient())
{
var response = await httpClient.PostAsync(uri, httpContent);
response.EnsureSuccessStatusCode();
resultStream = await response.Content.ReadAsStringAsync();
}
return resultStream;
}
Notes
If I remove the "messageContent" : It uploads he picture
If I use MultipartContent : It uploads the picture but ignores my "message"
Don't bother for now why I don't do use the async functionality
When it fails I get "bad" requests
When I append the "message=helloworld" in the requestUri, it works, but that isn't the most flexible solution for in my architecture to deal with this issue.

Check this it will solve you problem, either you have to send the image via stream then you don't need to tell that the type is "image/jpeg" explicitly.
protected async void TakePictureAndUpload()
{
var ui = new CameraCaptureUI();
var file = await ui.CaptureFileAsync(CameraCaptureUIMode.Photo);
if (file != null)
{
byte[] myPicArray = await GetPhotoBytesAsync(file);
HttpClient httpClient = new HttpClient();
httpClient.BaseAddress = new Uri("http://yourdomainname.com");
MultipartFormDataContent form = new MultipartFormDataContent();
HttpContent content = new ByteArrayContent(myPicArray);
form.Add(content, "media", "filename.jpg");
content = new StringContent("my-username");
form.Add(content, "username");
HttpResponseMessage response = await httpClient.PostAsync("directory/my-site.php", form);
}
}
public async Task<byte[]> GetPhotoBytesAsync(StorageFile file)
{
IRandomAccessStream fileStream = await file.OpenAsync(FileAccessMode.Read);
var reader = new Windows.Storage.Streams.DataReader(fileStream.GetInputStreamAt(0));
await reader.LoadAsync((uint)fileStream.Size);
byte[] pixels = new byte[fileStream.Size];
reader.ReadBytes(pixels);
return pixels;
}