/// <summary>
        /// 重试
        /// </summary>
        public class RetryHandler : DelegatingHandler
        {
            private const int maxRetries = 3;

            /// <summary>
            /// 重试
            /// </summary>
            /// <param name="innerHandler"></param>
            public RetryHandler(HttpMessageHandler innerHandler)
                : base(innerHandler)
            { }
            /// <summary>
            /// 重试
            /// </summary>
            /// <param name="request"></param>
            /// <param name="cancellationToken"></param>
            /// <returns></returns>
            protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
            {
                HttpResponseMessage response = null;
                for (int i = 0; i < maxRetries; i++)
                {
                    response = await base.SendAsync(request, cancellationToken);
                    if (response.IsSuccessStatusCode)
                    {
                        return response;
                    }
                }

                return response;
            }
        }

使用：

var client = new HttpClient(new RetryHandler(new HttpClientHandler())

Net中HttpClient 重试