C# HttpClient 4.5 multipart/form-data upload

Question

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.

Answer 1

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);
}