gistfile1.cs

[HttpGet]
public HttpResponseMessage ReadWidget(long id)
{
    WidgetBusiness widgetBusiness = new WidgetBusiness();
    Widget widget = widgetBusiness.Get(id);

    HttpResponseMessage response = new HttpResponseMessage();
    response.Content = new ByteArrayContent(widget.Data);
    response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
    response.Content.Headers.ContentDisposition.FileName = widget.Id.ToString();
    response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/jpg");
    return response;
}