Filter attribute to capture and log requests and responses in ASP.NET

CapturingResponseFilter.cs

class CapturingResponseFilter : Stream
{
    private Stream _sink;
    private MemoryStream mem;

    public APIAccessLogItem AccessLogItem { get; set; }

    public CapturingResponseFilter(Stream sink, APIAccessLogItem item)
    {
        _sink = sink;
        AccessLogItem = item;
        mem = new MemoryStream();
    }

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

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

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

    public override long Length
    {
        get { return _sink.Length; }
    }

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

    public override long Seek(long offset, SeekOrigin direction)
    {
        return _sink.Seek(offset,direction);
    }

    public override void SetLength(long length)
    {
        _sink.SetLength(length);
    }

    public override void Close()
    {
        _sink.Close();
        mem.Close();
    }

    public override void Flush()
    {
        _sink.Flush();

        AccessLogItem.ResponseBody = GetContents(new UTF8Encoding(false));
        //YOU CAN STORE YOUR DATA TO YOUR DATABASE HERE
    }

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

    public override void Write(byte[] buffer, int offset, int count)
    {
        mem.Write(buffer, 0, count);
        _sink.Write(buffer, offset, count);
    }

    public string GetContents(Encoding enc)
    {
        var buffer = new byte[mem.Length];
        mem.Position = 0;
        mem.Read(buffer, 0, buffer.Length);
        return enc.GetString(buffer, 0, buffer.Length);
    }
}

LoggerFilterAttribute.cs

public class LoggerFilterAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        base.OnActionExecuting(filterContext);

        HttpRequestBase request = filterContext.HttpContext.Request;

        APIAccessLogItem item;

        try
        {

            var controller = filterContext.Controller;
            var routeData = request.RequestContext.RouteData;
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < request.Headers.Count; i++)
                sb.AppendFormat("{0}={1};", request.Headers.Keys[i],
                                            request.Headers[i].ToString());

            item = new APIAccessLogItem()
            {
                RequestDate = DateTime.Now,
                RequestType = request.RequestType,
                Url = request.RawUrl,
                IPAddress = request.UserHostAddress,
                Controller = (string)routeData.Values["controller"],
                Action = (string)routeData.Values["action"],
                RequestHeader = sb.ToString()
            };

            sb = null;

            using (StreamReader reader = new StreamReader(request.InputStream))
            {
                try
                {
                    request.InputStream.Position = 0;
                    item.RequestBody = reader.ReadToEnd();
                }
                catch (Exception ex)
                {
                    item.RequestBody = string.Empty;
                    //log errors
                }
                finally
                {
                    request.InputStream.Position = 0;
                }
            }

            filterContext.HttpContext.Response.Filter = new CapturingResponseFilter(filterContext.HttpContext.Response.Filter, item);
        }
        catch (Exception ex)
        {
            //log errors
        }
    }

    public override void OnResultExecuted(ResultExecutedContext filterContext)
    {
        base.OnResultExecuted(filterContext);

        try
        {
            HttpResponseBase response = filterContext.HttpContext.Response;
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < response.Headers.Count; i++)
                sb.AppendFormat("{0}={1};", response.Headers.Keys[i], 
                                            response.Headers[i].ToString());

            var filter = (CapturingResponseFilter)filterContext.HttpContext.Response.Filter;
            var item = filter.AccessLogItem;

            item.ResponseDate = DateTime.Now;
            item.ResponseHeader = sb.ToString();

            sb = null;
        }
        catch (Exception ex)
        {
            //log errors
        }
    }
}