Convert HttpContent into byte[]

if (!content.IsMimeMultipartContent())
{
    throw new UnsupportedMediaTypeException("MIME Multipart Content is not supported");
}

var uploadPath = **whatever**;
if (!Directory.Exists(uploadPath))
{
    Directory.CreateDirectory(uploadPath);
}

var provider = new MultipartFormDataStreamProvider(uploadPath);
await content.ReadAsMultipartAsync(provider);

return File.ReadAllBytes(provider.FileData[0].LocalFileName);

HttpContent has a Async method which return ByteArray i.e (Task of ByteArray)

 Byte[] byteArray = await Content.ReadAsByteArrayAsync();

You can run the method synchronously

Byte[] byteArray = Content.ReadAsByteArrayAsync().Result;