我如何要求Owin/Katana将标头写入输出流？

Question

当我写回复时,Katana会跳过发送Elapsed-Time响应头.在我第一次写入流之前,如何让它为我设置标题？

中间件#1

    public override async Task Invoke(IOwinContext context)
    {
        var stopwatch = new Stopwatch();

        stopwatch.Start();
        await Next.Invoke(context);
        stopwatch.Stop();

        context.Response.Headers.Add("Elapsed-Time", new[] {stopwatch.ElapsedMilliseconds.ToString()});
    }

中间件#2

    public override async Task Invoke(IOwinContext context)
    {
        await context.Response.WriteAsync("test");
    }

Answer 1

经过一些研究,答案是设置标题需要在OnSendingHeaders中发生.这可确保在写入输出流之前设置标头.例如:

    public override async Task Invoke(IOwinContext context)
    {
        var stopwatch = new Stopwatch();

        context.Response.OnSendingHeaders(x =>
        {
            stopwatch.Stop();
            context.Response.Headers.Add("X-Processing-Time", new[] {stopwatch.ElapsedMilliseconds.ToString()});
        }, null);

        stopwatch.Start();
        await Next.Invoke(context);
        stopwatch.Stop();
    }