最近这段时间除了工作，所有的时间都是在移植我以前实现的一个Owin框架，相当移植到到Core的话肯定会有很多坑，这个大家都懂，以后几篇文章可能会围绕这个说下，暂时就叫《Dotnet Core踩坑记》吧，呵呵。

　　ASP.NET vNext刚推出的时候，号称是Owin的一个实现，在  上，直到现在还保留着这样一段描述。

　　Implementations

　　很多开发者纷纷实现着自己的Owin框架，也写很多应用到了实际的生产环境中，当然我也是其中一员。

　　移植过程中，会发现有很多的不同，还有遇到新的API不知道怎么使用，这时候看文档还不如直接看源码来的痛快。

　　在看完AspCore.Mvc后才发现，一点关于Owin的内容都没有；但很明显官方文档上说是支持Owin协议的，后来我硬着头皮去看了看KestrelHttpServer和HttpAbstractions两个项目，后来才发现原来真的没有一点点的Owin协议内容啊（一定要给MS差评）。

　　好吧，只能看看MS是怎么支持Owin的，在HttpAbstractions项目里发现了Microsoft.AspNetCore.Owin这样一个子项目，看完只是想说：“你这意思这叫向下兼容？” ，算了。 现在只要在Asp.net core项目里加入依赖Microsoft.AspNet.Owin就可以IApplicationBuilder接口的扩展方法UseOwin进行Owin中间件的调用。如下：

　　添加依赖：

"dependencies": { "Microsoft.AspNet.Server.Kestrel": "1.0.0-*", "Microsoft.AspNet.Owin": "1.0.0-*" },

　　在Startup中加入UseOwin：

Configure(IApplicationBuilder app) 2 { 3 app.UseOwin(pipeline => 4 { 5 pipeline(next => OwinHello); 6 }); 7 }

　　当然OwinHello的内容一定是一个标准Owin中间件的内容了：

1 public Task OwinHello(IDictionary<string, object> environment) 2 { ; 4 byte[] responseBytes = Encoding.UTF8.GetBytes(responseText); ]; ]; ] = new string[] { responseBytes.Length.ToString(CultureInfo.InvariantCulture) }; ] = }; 9 return responseStream.WriteAsync(responseBytes, 0, responseBytes.Length); 10 }

　　既然新的服务器已经不在支持Owin协议了，那个是怎么通信的？

　　这个问题在ASP.NET Core管道深度剖析系列文章中被提到过一些，其实每一个HttpContext在被创建出来都会依赖一个IFeatureCollection集合。

　　IFeatureCollection这个接口用于描述某个对象所具有的一组特征，由一组Feature接口组成。

　　列出其中一个IHttpConnectionFeature接口，用于获得Http的连接信息：

public class HttpConnectionFeature : IHttpConnectionFeature { public string ConnectionId { get; set; } public IPAddress LocalIpAddress { get; set; } public int LocalPort { get; set; } public IPAddress RemoteIpAddress { get; set; } public int RemotePort { get; set; } }

　　阅读kestrel源码，发现每一次接受tcp连接，都会将Http流，封装在一个帧Frame，它被描述成一个单向或双向的request和response。 并组装成特征集合供上层应用进行使用。

　　最后就发一段Owin字典对应Feature的源码吧：

_entries = new Dictionary<string, FeatureMap>() { { OwinConstants.RequestProtocol, new FeatureMap<IHttpRequestFeature>(feature => feature.Protocol, () => string.Empty, (feature, value) => feature.Protocol = Convert.ToString(value)) }, { OwinConstants.RequestScheme, new FeatureMap<IHttpRequestFeature>(feature => feature.Scheme, () => string.Empty, (feature, value) => feature.Scheme = Convert.ToString(value)) }, { OwinConstants.RequestMethod, new FeatureMap<IHttpRequestFeature>(feature => feature.Method, () => string.Empty, (feature, value) => feature.Method = Convert.ToString(value)) }, { OwinConstants.RequestPathBase, new FeatureMap<IHttpRequestFeature>(feature => feature.PathBase, () => string.Empty, (feature, value) => feature.PathBase = Convert.ToString(value)) }, { OwinConstants.RequestPath, new FeatureMap<IHttpRequestFeature>(feature => feature.Path, () => string.Empty, (feature, value) => feature.Path = Convert.ToString(value)) }, { OwinConstants.RequestQueryString, new FeatureMap<IHttpRequestFeature>(feature => Utilities.RemoveQuestionMark(feature.QueryString), () => string.Empty, (feature, value) => feature.QueryString = Utilities.AddQuestionMark(Convert.ToString(value))) }, { OwinConstants.RequestHeaders, new FeatureMap<IHttpRequestFeature>(feature => Utilities.MakeDictionaryStringArray(feature.Headers), (feature, value) => feature.Headers = Utilities.MakeHeaderDictionary((IDictionary<string, string[]>)value)) }, { OwinConstants.RequestBody, new FeatureMap<IHttpRequestFeature>(feature => feature.Body, () => Stream.Null, (feature, value) => feature.Body = (Stream)value) }, { OwinConstants.RequestUser, new FeatureMap<IHttpAuthenticationFeature>(feature => feature.User, () => null, (feature, value) => feature.User = (ClaimsPrincipal)value) }, { OwinConstants.ResponseStatusCode, new FeatureMap<IHttpResponseFeature>(feature => feature.StatusCode, () => 200, (feature, value) => feature.StatusCode = Convert.ToInt32(value)) }, { OwinConstants.ResponseReasonPhrase, new FeatureMap<IHttpResponseFeature>(feature => feature.ReasonPhrase, (feature, value) => feature.ReasonPhrase = Convert.ToString(value)) }, { OwinConstants.ResponseHeaders, new FeatureMap<IHttpResponseFeature>(feature => Utilities.MakeDictionaryStringArray(feature.Headers), (feature, value) => feature.Headers = Utilities.MakeHeaderDictionary((IDictionary<string, string[]>)value)) }, { OwinConstants.ResponseBody, new FeatureMap<IHttpResponseFeature>(feature => feature.Body, () => Stream.Null, (feature, value) => feature.Body = (Stream)value) },

　　只能说还好，性能并没有太多的损耗，粘的不全，全的自己看吧 : )