WebApi PostingFiles

gistfile1.cs

[ActionName("Index"), HttpPost]
public async Task<HttpResponseMessage> CreateAttachment(...)
{
    if (!Request.Content.IsMimeMultipartContent())
    {
        throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
    } 

    string attachmentsDirectoryPath = HttpContext.Current.Server.MapPath("~/SomeDir/");
    if (!Directory.Exists(attachmentsDirectoryPath))
    {
        Directory.CreateDirectory(attachmentsDirectoryPath);
    }

    var provider = new MultipartFormDataStreamProvider(attachmentsDirectoryPath);
    var result = await Request.Content.ReadAsMultipartAsync(provider);
    if (result.FileData.Count < 1)
    {
        throw new HttpResponseException(HttpStatusCode.BadRequest);
    }
    
    var fileData = result.FileData.First();
    string filename = fileData.Headers.ContentDisposition.FileName;
    
    Do stuff ...

    File.Delete(fileData.LocalFileName);    
    return Request.CreateResponse(HttpStatusCode.Created, ...);
}