BundleConfig.cs

bundles.Add(new PreassembledJavaScriptBundle("~/Scripts/all.min.js", "~/bundles/site")
                .IncludeDirectory("~/Scripts/Site", "*.js", true));

PreassembledJavaScriptBundle.cs

   public class PreassembledJavaScriptBundle : Bundle
    {
        private string _virtualPathToPreassembedFile { get; set; }

        protected PreassembledJavaScriptBundle(string virtualPathToPreassembedFile)
        {
            SetupvirtualPathToPreassembedFile(virtualPathToPreassembedFile);
        }
        public PreassembledJavaScriptBundle(string virtualPathToPreassembedFile, string virtualPath, string cdnPath, params IBundleTransform[] transforms)
            : base(virtualPath, cdnPath, transforms)
        {
            SetupvirtualPathToPreassembedFile(virtualPathToPreassembedFile);
        }
        public PreassembledJavaScriptBundle(string virtualPathToPreassembedFile, string virtualPath, params IBundleTransform[] transforms)
            : this(virtualPathToPreassembedFile, virtualPath, null, transforms)
        {

        }
        public PreassembledJavaScriptBundle(string virtualPathToPreassembedFile, string virtualPath)
            : this(virtualPathToPreassembedFile, virtualPath, (string)null, null)
        {

        }
        public PreassembledJavaScriptBundle(string virtualPathToPreassembedFile, string virtualPath, string cdnPath)
            : this(virtualPathToPreassembedFile, virtualPath, cdnPath, null)
        {

        }

        public override BundleResponse GenerateBundleResponse(BundleContext context)
        {
            IEnumerable<BundleFile> bundleFiles = EnumerateFiles(context);
            bundleFiles = context.BundleCollection.IgnoreList.FilterIgnoredFiles(context, bundleFiles);
            bundleFiles = Orderer.OrderFiles(context, bundleFiles);
            if (EnableFileExtensionReplacements)
            {
                bundleFiles = context.BundleCollection.FileExtensionReplacementList.ReplaceFileExtensions(context, bundleFiles);
            }

            string fileContents;
            using (var reader = new StreamReader(BundleTable.VirtualPathProvider.GetFile(_virtualPathToPreassembedFile).Open()))
            {
                fileContents = reader.ReadToEnd();
            }

            var response = new BundleResponse(fileContents, bundleFiles);
            response.ContentType = "text/javascript";
            return response;
        }

        private void SetupvirtualPathToPreassembedFile(string virtualPathToPreassembedFile)
        {

            if (!BundleTable.VirtualPathProvider.FileExists(virtualPathToPreassembedFile))
                throw new FileNotFoundException(String.Format("Unable to load preassembed bundle file: {0}", virtualPathToPreassembedFile));
            _virtualPathToPreassembedFile = virtualPathToPreassembedFile;
        }
    }