WebAPI-HTTP編程模型-有解無憂

帶著問題去思考，大家好！
它是什么？它包含什么？它能干什么？

訊息

HTTP編程模型的核心就是訊息抽象，表示為：HttPRequestMessage,HttpResponseMessage.用于客戶端和服務端之間交換請求和回應訊息，

HttpMethod類包含了一組靜態屬性：

   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")

標頭

HttpRequestHeaders：包含請求標頭
HttpResponseHeaders：包含回應標頭
HttpContentHeaders：包含內容標頭

訊息內容

HttpContent包含了非虛擬公共方法

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

第一種方式用于推送方式訪問原始的訊息內容，將一個流傳遞給CopyAsync方法，然后把訊息內容推送到這個流中

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().拉取方式訪問，這個方法異步回傳一個流

            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-異步提供訊息內容的緩沖副本，ReadAsStringAsync回傳原始的位元組內容，ReadAsByteArrayAsync將內容解碼為字串回傳

當然也可以擴展為

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

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