HttpContextAccessor 在.Net 系统中生命周期是singleton。

每一个请求来的时候不是应该New 一个 Context 吗？

它的源码中用到了这个：AsyncLocal<int>

每一个线程会保存它的本地的值。相当于线程的内部变量。

下面代码会打印：

100,100
300,100
100,100
300,100

    static void Main(string[] args)
        {
             var _threadLocal = 0;
             AsyncLocal<int> _asyncLocal = new AsyncLocal<int>();


            Task.Run(() =>
            {
                Thread.Sleep(200);
                _asyncLocal.Value = 100;
                _threadLocal = 100;
                while (true)
                {
                    Thread.Sleep(2000);
                    Console.WriteLine(_asyncLocal.Value+ ","+ _threadLocal);
                }
            });

            Task.Run(() =>
            {
                Thread.Sleep(200);
                _asyncLocal.Value = 300;
                _threadLocal = 300;
                while (true)
                {
                    Thread.Sleep(2000);
                    Console.WriteLine(_asyncLocal.Value+ "," + _threadLocal);
                }
            });
}