[AllowAnonymous]
[HttpGet]
[Route("DownloadImage")]
public HttpResponseMessage DownloadFile(string fileName)
{

            string filePath = Properties.Settings.Default.Path;
            string fullPath = filePath + fileName;

    try
    {
        //Check if the file exists. If the file doesn't exist, throw a
  file not found exception
        if (!File.Exists(fullPath))
        {
            throw new HttpResponseException(HttpStatusCode.NotFound);
        }

        //Copy the source file stream to MemoryStream and close the filestream
        MemoryStream responseStream = new MemoryStream();
        Stream fileStream = File.Open(fullPath, FileMode.Open);

        fileStream.CopyTo(responseStream);
        fileStream.Close();
        responseStream.Position = 0;

        HttpResponseMessage response = new HttpResponseMessage();
        response.StatusCode = HttpStatusCode.OK;

        //Write the memory stream to HttpResponseMessage content
        response.Content = new StreamContent(responseStream);
       string contentDisposition = string.Concat("attachment;
       filename=", fileName);
       response.Content.Headers.ContentDisposition =
   ContentDispositionHeaderValue.Parse(contentDisposition);
        response.Content.Headers.ContentType =
           new MediaTypeHeaderValue("image/jpeg");
        return response;
    }
    catch
    {
        throw new
  HttpResponseException(HttpStatusCode.InternalServerError);
    }
}