ScriptalizedOutputAttribute

AdBanner.html

<ul>
    <li></li>
    <li></li>
</ul>

AdController.cs

public class AdController : ControllerBase
{
    [ScriptalizedOutput]
    public ActionResult StackBanner()
    {
        // ...
 
        return View();  // 這裡還是單純 render HTML 就好
    }
}

ExpectedResult.html

document.write("<ul><li></li><li></li></ul>");

HostScript.html

<script type="type/javascript" src="http://test-server/Ad/StackBanner"></script>

ScriptalizedOutputAttribute.cs

public class ScriptalizedOutputAttribute : ActionFilterAttribute
{
    public bool WrapScriptTag { get; set; }

    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
    }

    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        var response = filterContext.HttpContext.Response;

        response.Filter = new StreamFilter(response.Filter, s =>
        {
            s = Regex.Replace(s, @"(\r\n|\n|\r)", "\\n"); // 換行字元都改掉
            s = Regex.Replace(s, @"\""", "\\\"");      // 要考慮逸出字元

            if (WrapScriptTag)
            {
                return string.Format("<script type=\"text/javascript\">\n//<!--\ndocument.write(\"{0}\");\n//-->\n</script>", s);
            }

            return string.Format("document.write(\"{0}\");", s);
        });

        response.ContentType = "text/javascript";
    }

    class StreamFilter : Stream
    {
        private Stream _shrink;
        private Func<string, string> _filter;

        public StreamFilter(Stream shrink, Func<string, string> filter)
        {
            _shrink = shrink;
            _filter = filter;
        }

        public override bool CanRead { get { return true; } }
        public override bool CanSeek { get { return true; } }
        public override bool CanWrite { get { return true; } }
        public override void Flush() { _shrink.Flush(); }
        public override long Length { get { return 0; } }
        public override long Position { get; set; }
        public override int Read(byte[] buffer, int offset, int count)
        {
            return _shrink.Read(buffer, offset, count);
        }
        public override long Seek(long offset, SeekOrigin origin)
        {
            return _shrink.Seek(offset, origin);
        }
        public override void SetLength(long value)
        {
            _shrink.SetLength(value);
        }
        public override void Close()
        {
            _shrink.Close();
        }

        public override void Write(byte[] buffer, int offset, int count)
        {
            // capture the data and convert to string 
            byte[] data = new byte[count];
            Buffer.BlockCopy(buffer, offset, data, 0, count);
            string s = Encoding.UTF8.GetString(buffer);

            // filter the string
            s = _filter(s);

            // write the data to stream 
            byte[] outdata = Encoding.UTF8.GetBytes(s);
            _shrink.Write(outdata, 0, outdata.GetLength(0));
        }
    }
}