c#/.net HttpContext.Request.BodyReader(PipeReader)的读取方式

        public async Task<string> GetString()
        {
            // 防止中间件已经读取过数据
            Request.Body.Position = 0;
            do
            {
                ReadResult readResult = await Request.BodyReader.ReadAsync();
                try
                {
                    if (readResult.IsCompleted || readResult.IsCanceled)
                    {
                        if (readResult.Buffer.Length <= 0)
                        {
                            throw new Exception("Request body is empty.");
                        }
                        if (readResult.IsCanceled)
                        {
                            throw new Exception("Request body is canceled.");
                        }
                        return Encoding.UTF8.GetString(readResult.Buffer);
                    }
                }
                finally
                {
                    Request.BodyReader.AdvanceTo(readResult.Buffer.Start, readResult.Buffer.End);
                }
            } while (true);
        }