net core2.1 在过滤器中获取post的body参数

public class OperateLogFilter : ActionFilterAttribute
    {
        private Stopwatch Stopwatch { get; set; }

        public override void OnActionExecuting(ActionExecutingContext context)
        {
            base.OnActionExecuting(context);

            Stopwatch = new Stopwatch();
            Stopwatch.Start();
        }

        public override void OnActionExecuted(ActionExecutedContext context)
        {
            base.OnActionExecuted(context);
            Stopwatch.Stop();

            string apiName = context.ActionDescriptor.DisplayName;
            double elapsed = Stopwatch.Elapsed.TotalMilliseconds;

            // 获取请求参数
            HttpRequest request = context.HttpContext.Request;
            //-- 由于mvc里已经读过request.Body，现在它的position在末尾
            // 允许重新读body
            request.EnableRewind();
            // 将position置到开始位置
            request.Body.Position = 0;
            // 读取body的数据流，并转为string
            var reader = new StreamReader(request.Body);
            var contentFromBody = reader.ReadToEnd();
        }

    }