带着问题去思考，大家好！

它是什么？它包含什么？它能干什么？

消息

HTTP编程模型的核心就是消息抽象，表示为：HttPRequestMessage,HttpResponseMessage.用于客户端和服务端之间交换请求和响应消息。

HttpMethod类包含了一组静态属性：

private static readonly HttpMethod getMethod = new HttpMethod("GET"); private static readonly HttpMethod putMethod = new HttpMethod("PUT"); private static readonly HttpMethod postMethod = new HttpMethod("POST"); private static readonly HttpMethod deleteMethod = new HttpMethod("DELETE"); private static readonly HttpMethod headMethod = new HttpMethod("HEAD"); private static readonly HttpMethod optionsMethod = new HttpMethod("OPTIONS"); private static readonly HttpMethod traceMethod = new HttpMethod("TRACE")

标头

• HttpRequestHeaders：包含请求标头
• HttpResponseHeaders：包含响应标头
• HttpContentHeaders：包含内容标头

 

消息内容

HttpContent包含了非虚拟公共方法

• Task<string> ReadAsStringAsync()
• Task<byte[]> ReadAsByteArrayAsync()
• Task<Stream> ReadAsStreamAsync()
• Task CopyToAsync(Stream stream, TransportContext context)

第一种方式用于推送方式访问原始的消息内容。将一个流传递给CopyAsync方法，然后把消息内容推送到这个流中

using(car client=new HtppClient()) { var response= await client.GetAsync("",HttpCompletionOption.ResponseHeadersRead); response.EnsureSuccessStatusCode(); var ms=new MemorySteam(); await response.Content.CopyToAsync(ms); Assert.True(ms.Length>0); }

也可以使用ReadAsStreamAsync().拉取方式访问。这个方法异步返回一个流

using(var client=new HttpClient()) { var response = await client.GetAsync(""); response.EnsureSuccessStatusCode(); var steam = await response.Content.ReadAsStreamAsync(); var buffer = new byte[2 * 1024]; var len = await steam.ReadAsync(buffer, 0, buffer.Length); }

ReadAsStringAsync和ReadAsByteArrayAsync-异步提供消息内容的缓冲副本。ReadAsStringAsync返回原始的字节内容，ReadAsByteArrayAsync将内容解码为字符串返回

当然也可以扩展为

public override Task<object> ReadContentAsync(HttpRequestMessage request, IEnumerable<MediaTypeFormatter> formatters, IFormatterLogger formatterLogger)