yes.blog/Yes.Infrastructure/ViewEngine/HttpRequestMessageProperty.cs

namespace Yes.Infrastructure.ViewEngine
{
    public sealed class HttpRequestMessageProperty : IMessageProperty, IMergeEnabledMessageProperty
    {
        private TraditionalHttpRequestMessageProperty _traditionalProperty;
        private HttpRequestMessageBackedProperty _httpBackedProperty;
        private bool _initialCopyPerformed;
        private bool _useHttpBackedProperty;

        public HttpRequestMessageProperty()
            : this((IHttpHeaderProvider)null)
        {
        }

        internal HttpRequestMessageProperty(IHttpHeaderProvider httpHeaderProvider)
        {
            _traditionalProperty = new TraditionalHttpRequestMessageProperty(httpHeaderProvider);
            _useHttpBackedProperty = false;
        }

        internal HttpRequestMessageProperty(HttpRequestMessage httpRequestMessage)
        {
            _httpBackedProperty = new HttpRequestMessageBackedProperty(httpRequestMessage);
            _useHttpBackedProperty = true;
        }

        public static string Name
        {
            get { return "httpRequest"; }
        }

        public WebHeaderCollection Headers
        {
            get
            {
                return _useHttpBackedProperty ?
                    _httpBackedProperty.Headers :
                    _traditionalProperty.Headers;
            }
        }

        public string Method
        {
            get
            {
                return _useHttpBackedProperty ?
                    _httpBackedProperty.Method :
                    _traditionalProperty.Method;
            }

            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException(nameof(value));
                }

                if (_useHttpBackedProperty)
                {
                    _httpBackedProperty.Method = value;
                }
                else
                {
                    _traditionalProperty.Method = value;
                }
            }
        }

        public string QueryString
        {
            get
            {
                return _useHttpBackedProperty ?
                    _httpBackedProperty.QueryString :
                    _traditionalProperty.QueryString;
            }

            set
            {

                if (value == null)
                {
                    throw new ArgumentNullException(nameof(value));
                }

                if (_useHttpBackedProperty)
                {
                    _httpBackedProperty.QueryString = value;
                }
                else
                {
                    _traditionalProperty.QueryString = value;
                }
            }
        }

        public bool SuppressEntityBody
        {
            get
            {
                return _useHttpBackedProperty ?
                    _httpBackedProperty.SuppressEntityBody :
                    _traditionalProperty.SuppressEntityBody;
            }

            set
            {
                if (_useHttpBackedProperty)
                {
                    _httpBackedProperty.SuppressEntityBody = value;
                }
                else
                {
                    _traditionalProperty.SuppressEntityBody = value;
                }
            }
        }

        //private HttpRequestMessage HttpRequestMessage {
        //	get {
        //		if (_useHttpBackedProperty) {
        //			return _httpBackedProperty.HttpRequestMessage;
        //		}

        //		return null;
        //	}
        //}

        //internal static HttpRequestMessage GetHttpRequestMessageFromMessage(Message message) {
        //	HttpRequestMessage httpRequestMessage = null;

        //	HttpRequestMessageProperty property = message.Properties.GetValue<HttpRequestMessageProperty>(HttpRequestMessageProperty.Name);
        //	if (property != null) {
        //		httpRequestMessage = property.HttpRequestMessage;
        //		if (httpRequestMessage != null) {
        //			httpRequestMessage.CopyPropertiesFromMessage(message);
        //			message.EnsureReadMessageState();
        //		}
        //	}

        //	return httpRequestMessage;
        //}

        IMessageProperty IMessageProperty.CreateCopy()
        {
            if (!_useHttpBackedProperty ||
                !_initialCopyPerformed)
            {
                _initialCopyPerformed = true;
                return this;
            }

            return _httpBackedProperty.CreateTraditionalRequestMessageProperty();
        }

        bool IMergeEnabledMessageProperty.TryMergeWithProperty(object propertyToMerge)
        {
            // The ImmutableDispatchRuntime will merge MessageProperty instances from the
            //  OperationContext (that were created before the response message was created) with
            //  MessageProperty instances on the message itself.  The message's version of the 
            //  HttpRequestMessageProperty may hold a reference to an HttpRequestMessage, and this 
            //  cannot be discarded, so values from the OperationContext's property must be set on 
            //  the message's version without completely replacing the message's property.
            if (_useHttpBackedProperty)
            {
                var requestProperty = propertyToMerge as HttpRequestMessageProperty;
                if (requestProperty != null)
                {
                    if (!requestProperty._useHttpBackedProperty)
                    {
                        _httpBackedProperty.MergeWithTraditionalProperty(requestProperty._traditionalProperty);
                        requestProperty._traditionalProperty = null;
                        requestProperty._httpBackedProperty = _httpBackedProperty;
                        requestProperty._useHttpBackedProperty = true;
                    }

                    return true;
                }
            }

            return false;
        }

        internal interface IHttpHeaderProvider
        {
            void CopyHeaders(WebHeaderCollection headers);
        }

        private class TraditionalHttpRequestMessageProperty
        {
            public const string DefaultMethod = "POST";
            public const string DefaultQueryString = "";

            private WebHeaderCollection _headers;
            private IHttpHeaderProvider _httpHeaderProvider;
            private string _method;

            public TraditionalHttpRequestMessageProperty(IHttpHeaderProvider httpHeaderProvider)
            {
                _httpHeaderProvider = httpHeaderProvider;
                _method = DefaultMethod;
                QueryString = DefaultQueryString;
            }

            public WebHeaderCollection Headers
            {
                get
                {
                    if (_headers == null)
                    {
                        _headers = new WebHeaderCollection();
                        if (_httpHeaderProvider != null)
                        {
                            _httpHeaderProvider.CopyHeaders(_headers);
                            _httpHeaderProvider = null;
                        }
                    }

                    return _headers;
                }
            }

            public string Method
            {
                get
                {
                    return _method;
                }

                set
                {
                    _method = value;
                    HasMethodBeenSet = true;
                }
            }

            public bool HasMethodBeenSet { get; private set; }

            public string QueryString { get; set; }

            public bool SuppressEntityBody { get; set; }
        }

        private class HttpRequestMessageBackedProperty
        {
            private HttpHeadersWebHeaderCollection _headers;

            public HttpRequestMessageBackedProperty(HttpRequestMessage httpRequestMessage)
            {
                HttpRequestMessage = httpRequestMessage ?? throw new ArgumentNullException(nameof(httpRequestMessage));
            }

            public HttpRequestMessage HttpRequestMessage { get; private set; }

            public WebHeaderCollection Headers
            {
                get
                {
                    if (_headers == null)
                    {
                        _headers = new HttpHeadersWebHeaderCollection(HttpRequestMessage);
                    }

                    return _headers;
                }
            }

            public string Method
            {
                get
                {
                    return HttpRequestMessage.Method.Method;
                }

                set
                {
                    HttpRequestMessage.Method = new HttpMethod(value);
                }
            }

            public string QueryString
            {
                get
                {
                    var query = HttpRequestMessage.RequestUri.Query;
                    return query.Length > 0 ? query.Substring(1) : string.Empty;
                }

                set
                {
                    var uriBuilder = new UriBuilder(HttpRequestMessage.RequestUri);
                    uriBuilder.Query = value;
                    HttpRequestMessage.RequestUri = uriBuilder.Uri;
                }
            }

            public bool SuppressEntityBody
            {
                get
                {
                    var content = HttpRequestMessage.Content;
                    if (content != null)
                    {
                        var contentLength = content.Headers.ContentLength;

                        if (!contentLength.HasValue || contentLength.Value > 0)
                        {
                            return false;
                        }
                    }

                    return true;
                }
                set
                {
                    var content = HttpRequestMessage.Content;
                    if (value && content != null &&
                        (!content.Headers.ContentLength.HasValue ||
                        content.Headers.ContentLength.Value > 0))
                    {
                        HttpContent newContent = new ByteArrayContent(EmptyArray<byte>.Instance);
                        foreach (var header in content.Headers)
                        {
                            newContent.Headers.TryAddWithoutValidation(header.Key, header.Value);
                        }

                        HttpRequestMessage.Content = newContent;
                        content.Dispose();
                    }
                    else if (!value && content == null)
                    {
                        HttpRequestMessage.Content = new ByteArrayContent(EmptyArray<byte>.Instance);
                    }
                }
            }

            public HttpRequestMessageProperty CreateTraditionalRequestMessageProperty()
            {
                var copiedProperty = new HttpRequestMessageProperty();

                copiedProperty.Headers.Add(Headers);

                if (Method != TraditionalHttpRequestMessageProperty.DefaultMethod)
                {
                    copiedProperty.Method = Method;
                }

                copiedProperty.QueryString = QueryString;
                copiedProperty.SuppressEntityBody = SuppressEntityBody;

                return copiedProperty;
            }

            public void MergeWithTraditionalProperty(TraditionalHttpRequestMessageProperty propertyToMerge)
            {
                if (propertyToMerge.HasMethodBeenSet)
                {
                    Method = propertyToMerge.Method;
                }

                if (propertyToMerge.QueryString != TraditionalHttpRequestMessageProperty.DefaultQueryString)
                {
                    QueryString = propertyToMerge.QueryString;
                }

                SuppressEntityBody = propertyToMerge.SuppressEntityBody;

                var headersToMerge = propertyToMerge.Headers;
                foreach (var headerKey in headersToMerge.AllKeys)
                {
                    Headers[headerKey] = headersToMerge[headerKey];
                }
            }
        }
    }
}