在中间件中使用.NET Core会话

Question

当我在.NET Core中编写可缩短链并返回响应的中间件时，它不会设置会话cookie。一个简短的例子：

public class Middleware
{

    private RequestDelegate _next;

    public Middleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        var req = context.Request;
        if (req.Path.ToString() == "/hello-world")
        {
            context.Response.StatusCode = 200;
            context.Response.Headers["Content-Type"] = "text/html; charset=utf-8";
            await context.Response.WriteAsync("Hello, world!");
            return;
        }

        await _next(context);

    }

}

这是我Startup班上的相关代码：

public class Startup
{

    public void ConfigureServices(IServiceCollection services)
    {
        services
            .AddDistributedMemoryCache()
            .AddSession();
    }

    public void Configure(IApplicationBuilder app)
    {
        app
            .UseSession()
            .UseMiddleware<Middleware>();
    }
}

传递响应头：

HTTP 200 No Error

Server: Kestrel
Set-Cookie: .AspNetCore.Session=CfDJ8C1XpX5nCrFCnHz%2BDwlF41YjVSyPMqB8Qmk6qcDPnOSpG22yun3hsXpRBgMDhlX%2ByLbqkUtqPRYY%2B1%2Bno5WeRLnabM1zBDggvB4YEg6ooBiGN%2B5ktjjgfp4uH5mmlWZpEQyQJQb0vKDGwqWpMlLEGjMxVIMqOnkqjM0DvsQIPjt6; path=/; samesite=lax; httponly
Content-Type: text/html; charset=utf-8
Pragma: no-cache
Transfer-Encoding: Identity
Date: Thu, 18 Jan 2018 20:48:55 GMT
Expires: -1
Cache-Control: no-cache

短路响应头：

HTTP 200 No Error

Transfer-Encoding: Identity
Content-Type: text/html; charset=utf-8
Server: Kestrel
Date: Thu, 18 Jan 2018 21:17:39 GMT

简而言之，我需要知道为什么会话中间件没有发送回cookie。加载页面时，我也似乎收到一些会话警告，提示无法解码Cookie。

Answer 1

我没有向会话添加任何内容，因此中间件没有创建会话。只需添加context.Session.SetString("stuff", "3");（或 Set* 变体之一）即可将会话发送到客户端。您需要在写入响应正文之前执行此操作。