ASP.NET WebApi: how to perform a multipart post with file upload using WebApi HttpClient

Question

I have a WebApi service handling an upload from a simple form, like this one:

Answer 1

You need to look for various subclasses of HttpContent.

You create a multiform http content and add various parts to it. In your case you have a byte array content and form url encoded along the lines of:

HttpClient c = new HttpClient();
var fileContent = new ByteArrayContent(new byte[100]);
fileContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
                                            {
                                                FileName = "myFilename.txt"
                                            };

var formData = new FormUrlEncodedContent(new[]
                                            {
                                                new KeyValuePair("name", "ali"),
                                                new KeyValuePair("title", "ostad")
                                            });


MultipartContent content = new MultipartContent();
content.Add(formData);
content.Add(fileContent);
c.PostAsync(myUrl, content);