How to send and receive multipart/form-data containing files in .NET Core? - asp.net-core

Question

Using .NET Core 3.1, I have the following Http client which builds a HTTP POST containing multipart/form-data body:
public async Task SendRequest(string randomString, IFormFileCollection files)
{
var form = new MultipartFormDataContent();
form.Add(new StringContent(randomString), "randomString");
foreach (var file in files)
{
var stream = new MemoryStream();
await file.CopyToAsync(stream, cancellationToken);
form.Add(new StreamContent(stream), "files");
}
using var request = new HttpRequestMessage(HttpMethod.Post, $"api/endpoint")
{
Content = form
};
await _httpClient.SendAsync(request);
}
The receiving controller looks like this:
[Consumes("multipart/form-data")]
[HttpPost]
public async Task ReceiveForm([FromForm] RequestModel request)
{
//Do stuff
}
RequestModel looks like this:
public class RequestModel
{
[JsonPropertyName("randomString")]
public string RandomString { get; set; }
[JsonPropertyName("files")]
public IFormFileCollection Files { get; set; }
}
The problem I am seeing is that requestModel.RandomString gets populated, but the requestModel.Files does not - it is null.
What am I doing wrong?

Answer 1

thanks for the perfect code in example!
You should set both parameters (name and fileName) to files - form.Add(new StreamContent(stream), "files", "files");
Method description:
Parameters:
content: The HTTP content to add to the collection.
name: The name for the HTTP content to add.
fileName: The file name for the HTTP content to add to the collection.
This is my example:
var fileName = "files";
var byteArrayContent = new ByteArrayContent(fileBytes1);
form.Add(byteArrayContent, fileName, fileName);
var stream = new MemoryStream(fileBytes2);
form.Add(new StreamContent(stream), fileName, fileName);
Results: