Как использовать Универсальные Обработчики (ASHX) в ASP.NET MVC?

Вы также можете использовать этот класс ImageResult для возврата изображения.

Нет необходимости в обработчике, просто создайте маршрут, например:

/ ImageGenerator / {action} / {imageid} /

и верните ImageResult для запроса.

 public class ImageResult : ActionResult
    {
        public string SourceFilename { get; set; }
        public MemoryStream SourceStream { get; set; }
        public string ContentType { get; set; }
        public ImageResult(string sourceFilename)
        {
            SourceFilename = sourceFilename;
            ContentType = FileTypeHelper.GetContentType(SourceFilename);
        }
        public ImageResult(MemoryStream sourceStream, string contentType)
        {
            SourceStream = sourceStream;
            ContentType = contentType;
        }
        public override void ExecuteResult(ControllerContext context)
        {   
            var res = context.HttpContext.Response;
            res.Clear();
            res.Cache.SetCacheability(HttpCacheability.NoCache);
            res.ContentType = ContentType;

            if (SourceStream != null)
            {
                SourceStream.WriteTo(res.OutputStream);

            }
            else
            {
               res.TransmitFile(SourceFilename);
            }

        }


    }

Чтобы использовать это, сделайте следующее в контроллере и добавьте для него маршрут:

public ImageResult GetImage(int imageId)
{
   // Database fetch of image details
   var imageInfo = repository.Get<ImageInfo>(imageId);
   return new ImageResult(imageInfo.FullFilename);
}

Также добавили вспомогательный класс FileType:

 public static class FileTypeHelper
{
    public static string GetContentType(string SourceFileName)
    {
        var extension = Path.GetExtension(SourceFileName).ToLower();
         switch (extension)
        {
            case ".ai": return "application/postscript";
            case ".aif": return "audio/x-aiff";
            case ".aifc": return "audio/x-aiff";
            case ".aiff": return "audio/x-aiff";
            case ".asc": return "text/plain";
            case ".au": return "audio/basic";
            case ".avi": return "video/x-msvideo";
            case ".bcpio": return "application/x-bcpio";
            case ".bin": return "application/octet-stream";
            case ".c": return "text/plain";
            case ".cc": return "text/plain";
            case ".ccad": return "application/clariscad";
            case ".cdf": return "application/x-netcdf";
            case ".class": return "application/octet-stream";
            case ".cpio": return "application/x-cpio";
            case ".cpp": return "text/plain";
            case ".cpt": return "application/mac-compactpro";
            case ".cs": return "text/plain";
            case ".csh": return "application/x-csh";
            case ".css": return "text/css";
            case ".dcr": return "application/x-director";
            case ".dir": return "application/x-director";
            case ".dms": return "application/octet-stream";
            case ".doc": return "application/msword";
            case ".drw": return "application/drafting";
            case ".dvi": return "application/x-dvi";
            case ".dwg": return "application/acad";
            case ".dxf": return "application/dxf";
            case ".dxr": return "application/x-director";
            case ".eps": return "application/postscript";
            case ".etx": return "text/x-setext";
            case ".exe": return "application/octet-stream";
            case ".ez": return "application/andrew-inset";
            case ".f": return "text/plain";
            case ".f90": return "text/plain";
            case ".fli": return "video/x-fli";
            case ".flv": return "video/x-flv";
            case ".gif": return "image/gif";
            case ".gtar": return "application/x-gtar";
            case ".gz": return "application/x-gzip";
            case ".h": return "text/plain";
            case ".hdf": return "application/x-hdf";
            case ".hh": return "text/plain";
            case ".hqx": return "application/mac-binhex40";
            case ".htm": return "text/html";
            case ".html": return "text/html";
            case ".ice": return "x-conference/x-cooltalk";
            case ".ief": return "image/ief";
            case ".iges": return "model/iges";
            case ".igs": return "model/iges";
            case ".ips": return "application/x-ipscript";
            case ".ipx": return "application/x-ipix";
            case ".jpe": return "image/jpeg";
            case ".jpeg": return "image/jpeg";
            case ".jpg": return "image/jpeg";
            case ".js": return "application/x-javascript";
            case ".kar": return "audio/midi";
            case ".latex": return "application/x-latex";
            case ".lha": return "application/octet-stream";
            case ".lsp": return "application/x-lisp";
            case ".lzh": return "application/octet-stream";
            case ".m": return "text/plain";
            case ".man": return "application/x-troff-man";
            case ".me": return "application/x-troff-me";
            case ".mesh": return "model/mesh";
            case ".mid": return "audio/midi";
            case ".midi": return "audio/midi";
            case ".mime": return "www/mime";
            case ".mov": return "video/quicktime";
            case ".movie": return "video/x-sgi-movie";
            case ".mp2": return "audio/mpeg";
            case ".mp3": return "audio/mpeg";
            case ".mpe": return "video/mpeg";
            case ".mpeg": return "video/mpeg";
            case ".mpg": return "video/mpeg";
            case ".mpga": return "audio/mpeg";
            case ".ms": return "application/x-troff-ms";
            case ".msh": return "model/mesh";
            case ".nc": return "application/x-netcdf";
            case ".oda": return "application/oda";
            case ".pbm": return "image/x-portable-bitmap";
            case ".pdb": return "chemical/x-pdb";
            case ".pdf": return "application/pdf";
            case ".pgm": return "image/x-portable-graymap";
            case ".pgn": return "application/x-chess-pgn";
            case ".png": return "image/png";
            case ".pnm": return "image/x-portable-anymap";
            case ".pot": return "application/mspowerpoint";
            case ".ppm": return "image/x-portable-pixmap";
            case ".pps": return "application/mspowerpoint";
            case ".ppt": return "application/mspowerpoint";
            case ".ppz": return "application/mspowerpoint";
            case ".pre": return "application/x-freelance";
            case ".prt": return "application/pro_eng";
            case ".ps": return "application/postscript";
            case ".qt": return "video/quicktime";
            case ".ra": return "audio/x-realaudio";
            case ".ram": return "audio/x-pn-realaudio";
            case ".ras": return "image/cmu-raster";
            case ".rgb": return "image/x-rgb";
            case ".rm": return "audio/x-pn-realaudio";
            case ".roff": return "application/x-troff";
            case ".rpm": return "audio/x-pn-realaudio-plugin";
            case ".rtf": return "text/rtf";
            case ".rtx": return "text/richtext";
            case ".scm": return "application/x-lotusscreencam";
            case ".set": return "application/set";
            case ".sgm": return "text/sgml";
            case ".sgml": return "text/sgml";
            case ".sh": return "application/x-sh";
            case ".shar": return "application/x-shar";
            case ".silo": return "model/mesh";
            case ".sit": return "application/x-stuffit";
            case ".skd": return "application/x-koan";
            case ".skm": return "application/x-koan";
            case ".skp": return "application/x-koan";
            case ".skt": return "application/x-koan";
            case ".smi": return "application/smil";
            case ".smil": return "application/smil";
            case ".snd": return "audio/basic";
            case ".sol": return "application/solids";
            case ".spl": return "application/x-futuresplash";
            case ".src": return "application/x-wais-source";
            case ".step": return "application/STEP";
            case ".stl": return "application/SLA";
            case ".stp": return "application/STEP";
            case ".sv4cpio": return "application/x-sv4cpio";
            case ".sv4crc": return "application/x-sv4crc";
            case ".swf": return "application/x-shockwave-flash";
            case ".t": return "application/x-troff";
            case ".tar": return "application/x-tar";
            case ".tcl": return "application/x-tcl";
            case ".tex": return "application/x-tex";
            case ".tif": return "image/tiff";
            case ".tiff": return "image/tiff";
            case ".tr": return "application/x-troff";
            case ".tsi": return "audio/TSP-audio";
            case ".tsp": return "application/dsptype";
            case ".tsv": return "text/tab-separated-values";
            case ".txt": return "text/plain";
            case ".unv": return "application/i-deas";
            case ".ustar": return "application/x-ustar";
            case ".vcd": return "application/x-cdlink";
            case ".vda": return "application/vda";
            case ".vrml": return "model/vrml";
            case ".wav": return "audio/x-wav";
            case ".wrl": return "model/vrml";
            case ".xbm": return "image/x-xbitmap";
            case ".xlc": return "application/vnd.ms-excel";
            case ".xll": return "application/vnd.ms-excel";
            case ".xlm": return "application/vnd.ms-excel";
            case ".xls": return "application/vnd.ms-excel";
            case ".xlw": return "application/vnd.ms-excel";
            case ".xml": return "text/xml";
            case ".xpm": return "image/x-xpixmap";
            case ".xwd": return "image/x-xwindowdump";
            case ".xyz": return "chemical/x-pdb";
            case ".zip": return "application/zip";
            default: return string.Format("application/{0}", extension);
        }
    }
}