ASP.NET Core – 读写 Request / Response

需求

常见的需求就是从 request 里面读取一些 information. 比如 

request URL, header, cookie, 

写入 response header, cookie

实战

Razor Page Model 中

// 读取 request, header, cookie
var fullUrl = HttpContext.Request.GetDisplayUrl(); // https://192.168.1.152:44300/?value=v1&value=v2 (note: about 的话是 .../about?value=v1, 不是 .../about/?value=v1 哦)
var scheme = HttpContext.Request.Scheme; // https
var host = HttpContext.Request.Host.Host; // 192.168.1.152
var port = HttpContext.Request.Host.Port; // 44300
var path = HttpContext.Request.Path; // "/" <-- home page 的 path 是 /
var queryString = HttpContext.Request.QueryString.Value; // ?value=v1&value=v2
var query = HttpContext.Request.Query;
if (query.TryGetValue("value", out StringValues value))
{
    // same key won't combine
    var value1 = value.ElementAt(0); // v1
    var value2 = value.ElementAt(1); // v2
    var combineValue =  value.ToString(); // v1,v2
}
var remoteIp = HttpContext.Connection.RemoteIpAddress;

if (HttpContext.Request.Cookies.TryGetValue("cookie1", out var cookieValue)) 
{ 
        
}
var userAgent = HttpContext.Request.Headers.UserAgent.ToString();
var contentType = HttpContext.Request.Headers.ContentType.ToString();
if (HttpContext.Request.Headers.TryGetValue("Custom-Header", out StringValues customHeaderValue)) // h1,h2
{
    var h1 = customHeaderValue.ElementAt(0); // h1,h2
    var h2 = customHeaderValue.ElementAtOrDefault(1); // null
    var combineHeader = customHeaderValue.ToString(); // h1,h2
    // same key will combine become value1 value2
};

// 写入 header, cookie
HttpContext.Response.Headers.Add("CustomResponseHeader", "value1");
HttpContext.Response.Cookies.Append("cookie1", "value1");

可以看到关键就是 HttpContext, request, response 都可以通过这个去读写.

header 和 query 如果遇到有 2 个 key (虽然我不知道什么情况下会需要这样), header 是会 combine value 而 query 是不会的哦 

queryString 获取的值就是 original 的值, 是含 encode 的, 调用 TryGetValue 的时候我们则不需要顾虑 encode, decode, 它会替我们处理好.

更多关于 query 的操控可以看这篇

razor .cshtml

我们依然可以调用到 HttpContext

@HttpContext.Request.Headers.UserAgent

Web API Controller

var userAgent = HttpContext.Request.Headers.UserAgent;

DI Service

要在 service 中获取到 Httpcontext 就需要依赖注入. 

首先在 startup.cs

services.AddHttpContextAccessor();

然后在 Service.cs, 通过 HttpContextAccessor 就可以获取到 HttpContext 了

public class CustomerService
{
    private readonly HttpContext _httpContext;
    public CustomerService(
      IHttpContextAccessor httpContextAccessor
    )
    {
        _httpContext = httpContextAccessor.HttpContext!;
    }

    public string GetUserAgent() 
    { 
        return _httpContext.Request.Headers.UserAgent;
    }
}