{"id":221291,"date":"2021-07-03T08:45:46","date_gmt":"2021-07-03T00:45:46","guid":{"rendered":"https:\/\/lrxjmw.cn\/?p=221291"},"modified":"2021-06-25T09:47:02","modified_gmt":"2021-06-25T01:47:02","slug":"reduce-nested-loops","status":"publish","type":"post","link":"https:\/\/lrxjmw.cn\/reduce-nested-loops.html","title":{"rendered":"C# \u5982\u4f55\u51cf\u5c11\u5d4c\u5957\u5faa\u73af"},"content":{"rendered":"<table>\n<tbody>\n<tr>\n<td style=\"padding: 5px 12px; width: 25px; font-size: 22px; text-align: center; background: #E8E8E8; line-height: 30px; color: #999;\">\u5bfc\u8bfb<\/td>\n<td style=\"padding: 10px 10px 12px; line-height: 20px;\"><strong>\u6700\u8fd1\u5728\u89e3\u51b3\u6027\u80fd\u4f18\u5316\u7684\u95ee\u9898\uff0c\u770b\u5230\u4e86\u4e00\u5806\u5d4c\u5957\u5faa\u73af\uff0c\u56db\u4e94\u5c42\u7ea7\u7684\u5faa\u73af\u771f\u7684\u6709\u70b9\u8fc7\u5206\u4e86\uff0c\u5728\u6570\u636e\u91cf\u6210\u4e07\uff0c\u5341\u4e07\u7ea7\u522b\u7684\u65f6\u5019\uff0c\u771f\u7684\u975e\u5e38\u5f71\u54cd\u6027\u80fd\u3002\u672c\u6587\u4ecb\u7ecd\u4e86C# \u51cf\u5c11\u5d4c\u5957\u5faa\u73af\u7684\u4e24\u79cd\u65b9\u6cd5\uff0c\u5e2e\u52a9\u5404\u4f4d\u9009\u62e9\u9002\u5408\u81ea\u5df1\u7684\u4f18\u5316\u65b9\u6848\uff0c\u4f18\u5316\u7a0b\u5e8f\u6027\u80fd<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u5f53\u7136\uff0c\u9664\u4e86\u5173\u6ce8\u660e\u663e\u7684\u5faa\u73af\u4f8b\u5982for\u3001foreach\uff0c\u8fd8\u5e94\u8be5\u5173\u6ce8\u9690\u6666\u4e00\u70b9\u7684\u5faa\u73af\uff0c\u4f8b\u5982datatable.select()\uff0clinq\u4e4b\u7c7b\u7684list.where\u3001list.find\u7b49\u3002<\/p>\n<p>\u8981\u4f18\u5316\uff0c\u6392\u9664\u4e1a\u52a1\u95ee\u9898\uff0c\u8981\u8003\u8651\u7684\u5c31\u662f\u4ee3\u7801\u6280\u672f\u4e86\u3002\u770b\u5230\u5faa\u73af\u67e5\u627e\u6570\u636e\uff0c\u5c3d\u53ef\u80fd\u5411Dictionary\u9760\u62e2\u3002<\/p>\n<div   id="j6sjwn9j3u"    style=\"font-size: 14pt; color: white; background-color: black; border-left: red 10px solid; padding-left: 14px; margin-bottom: 20px; margin-top: 20px;\"><strong>eg1\uff1a\u4e00\u4e2a\u7b80\u5355\u7684key\u5bf9\u5e94\u4e00\u6761datarow<\/strong><\/div>\n<p><strong>\u4f18\u5316\u524d\uff1a<\/strong><\/p>\n<pre>\r\nusing System.Linq;\r\n \r\nnamespace ConsoleApp1\r\n{\r\n    internal class Program\r\n    {\r\n        private static void Main(string[] args)\r\n        {\r\n            DataTable table = new DataTable();\r\n            ...\r\n            for (int i = 0; i < 1000000; i++)\r\n            {\r\n                var row = table.AsEnumerable().FirstOrDefault(r => r[\"num\"].ToString() == i.ToString());\r\n                ...\r\n            }\r\n        }\r\n    }\r\n}\r\n<\/pre>\n<p><strong>\u4f18\u5316\u540e\uff1a<\/strong><\/p>\n<pre>\r\nusing System.Data;\r\nusing System.Linq;\r\n \r\nnamespace ConsoleApp1\r\n{\r\n    internal class Program\r\n    {\r\n        private static void Main(string[] args)\r\n        {\r\n            DataTable table = new DataTable();\r\n            ...\r\n            var dict = table.AsEnumerable().ToDictionary(r => r[\"num\"].ToString());\r\n            for (int i = 0; i < 1000000; i++)\r\n            {\r\n                if (dict.ContainsKey(i.ToString()))\r\n                {\r\n                    var row = dict[i.ToString()];\r\n                }\r\n                ...\r\n            }\r\n        }      \r\n    }\r\n}\r\n<\/pre>\n<div   id="j6sjwn9j3u"    style=\"font-size: 14pt; color: white; background-color: black; border-left: red 10px solid; padding-left: 14px; margin-bottom: 20px; margin-top: 20px;\"><strong>eg2\uff1a\u4e00\u4e2a\u62fc\u88c5\u7684Key\u5bf9\u5e94\u591a\u6761DataRow\u7684\u5b57\u5178<\/strong><\/div>\n<p><strong>\u4f18\u5316\u524d\uff1a<\/strong><\/p>\n<pre>\r\nusing System.Data;\r\nusing System.Linq;\r\n \r\nnamespace ConsoleApp1\r\n{\r\n    internal class Program\r\n    {\r\n        private static void Main(string[] args)\r\n        {\r\n            DataTable table = new DataTable();   \r\n            ...\r\n            for (int i = 0; i < 1000000; i++)\r\n            {\r\n                var name = \"\";\r\n                ...\r\n                var rows = table.AsEnumerable().Where(r => r[\"num\"].ToString() == i.ToString() && r[\"name\"].ToString() == name);\r\n            }\r\n        }             \r\n    }\r\n}\r\n<\/pre>\n<p><strong>\u4f18\u5316\u540e\uff1a<\/strong><\/p>\n<pre>\r\nusing System.Data;\r\nusing System.Linq;\r\n \r\nnamespace ConsoleApp1\r\n{\r\n    internal class Program\r\n    {\r\n        private static void Main(string[] args)\r\n        {\r\n            DataTable table = new DataTable();\r\n            var group = table.AsEnumerable().GroupBy(r => GetGroupKey(r[\"num\"].ToString(), r[\"name\"].ToString()));\r\n            var dict= group.ToDictionary(r=>r.Key);\r\n            ...\r\n            for (int i = 0; i < 1000000; i++)\r\n            {\r\n                var name = \"\";\r\n                var key = GetGroupKey(i.ToString(), name);\r\n                if (dict.ContainsKey(key))\r\n                {\r\n                    var rows = dict[key];\r\n                }               \r\n                ...\r\n            }\r\n        }      \r\n        \r\n        private static string GetGroupKey(string _num,string _name)\r\n        {\r\n            return $\"num={_num}|name={_name}\";\r\n        }\r\n    }\r\n}<\/pre>\n<p>\u91cf\u53d8\u4f1a\u5f15\u8d77\u8d28\u53d8\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5f53\u7136\uff0c\u9664\u4e86\u5173\u6ce8\u660e\u663e\u7684\u5faa\u73af\u4f8b\u5982for\u3001foreach\uff0c\u8fd8\u5e94\u8be5\u5173\u6ce8\u9690\u6666\u4e00\u70b9\u7684\u5faa\u73af\uff0c\u4f8b\u5982datatable.sele [&hellip;]<\/p>\n","protected":false},"author":362,"featured_media":221292,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[55],"tags":[],"class_list":["post-221291","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-thread"],"acf":[],"_links":{"self":[{"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/posts\/221291","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/users\/362"}],"replies":[{"embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/comments?post=221291"}],"version-history":[{"count":2,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/posts\/221291\/revisions"}],"predecessor-version":[{"id":221294,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/posts\/221291\/revisions\/221294"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/media\/221292"}],"wp:attachment":[{"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/media?parent=221291"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/categories?post=221291"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lrxjmw.cn\/wp-json\/wp\/v2\/tags?post=221291"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}