Handling POST data from Chargify so that MVC model binding works...

ChargifyStreamDecorator.cs

 /// <summary>
    /// Filter that replaces [] with . so that model binding works.
    /// </summary>
    /// <remarks>
    /// simplistic - does a global replace. Also assumes that [, ] 
    /// are not url encoded in the key names (and this is 
    /// the case with chargify right now 
    /// so product name like 'Daily Plan []' is sent as
    /// payload[subscription][product][name]=Daily%20Plan%20%5B%5D
    /// ie key names square brackets are sent as is, whereas in values they are url encoded.
    ///
    /// 
    /// This filter does not handle arrays - but no chargify event has arrays.
    /// 
    /// attached to the Request.Filter in Global.asax for chargify events.
    /// </remarks>
    public class ChargifyStreamDecorator : Stream
    {
        private readonly Stream theStream;
        private Stream modifiedStream = null;
        private string documentContents;

        public ChargifyStreamDecorator(Stream orig)
        {
            this.theStream = orig;
        }

        public String OriginalContent
        {
            get
            {
                initialize();
                return this.documentContents;
            }
        }


        public override void Flush()
        {
            modifiedStream.Flush();
        }

        private void initialize()
        {
            // found that I cannot call this from the ctor since the actual stream return 0 length 
            // so calling this from read with the guard below
            if (this.modifiedStream != null) return;
            string documentContents;
            using (Stream receiveStream = theStream)
            {
                using (StreamReader readStream = new StreamReader(receiveStream, Encoding.UTF8))
                {
                    documentContents = readStream.ReadToEnd();
                }
            }
            // [ -> ., ] -> ""
            var modifiedContents = documentContents
                .Replace("[", ".").Replace("]", "");
            modifiedStream = new MemoryStream(Encoding.UTF8.GetBytes(modifiedContents));
        }

        public override long Seek(long offset, SeekOrigin origin)
        {
            return modifiedStream.Seek(offset, origin);
        }

        public override void SetLength(long value)
        {
            throw new NotSupportedException();
        }

        public override int Read(byte[] buffer, int offset, int count)
        {
            initialize();
            return modifiedStream.Read(buffer, offset, count);
        }

        public override void Write(byte[] buffer, int offset, int count)
        {
            throw new NotSupportedException();
        }

        public override bool CanRead
        {
            get { return theStream.CanRead; }
        }

        public override bool CanSeek
        {
            get { return theStream.CanSeek; }
        }

        public override bool CanWrite
        {
            get { return theStream.CanWrite; }
        }

        public override long Length
        {
            get { return this.modifiedStream.Length; }
        }

        public override long Position { get { return this.modifiedStream.Position; } set { this.modifiedStream.Position = value; } }
    }

Global.asax.cs

public class WebApiApplication : System.Web.HttpApplication
{
    public void Application_BeginRequest()
    {
        if (Request.Url.AbsolutePath.Contains("ChargifyEvents"))
        {
            Request.Filter = new ChargifyStreamDecorator(Request.Filter);
        }
    }
}