正则表达式入门及备忘

            string input = "Generic specialization, the decorator pattern, chains of responsibilities, and extensible software.";
            Regex reg = new Regex("pattern", RegexOptions.IgnoreCase);

            Console.WriteLine(reg.Matches(input).Count);  //output 1

            string input = "The color of shirt is gray and color of shoes is grey too.";
            Regex reg = new Regex("gr[ae]y", RegexOptions.IgnoreCase);

            Console.WriteLine(reg.Matches(input).Count);  //output 2

            var matchs = reg.Matches(input);
            foreach (Match match in matchs)
            {
                Console.WriteLine(match.Value);//output gray  grey
            }

            string input = "1024 hello world&%";
            Regex reg1 = new Regex(@"\d\d\d\d");
            if (reg1.IsMatch(input)) 
            {
                Console.WriteLine(reg1.Match(input).Value);//output 1024
            }

            Regex reg2 = new Regex(@"\W\W");
            if (reg2.IsMatch(input))
            {
                Console.WriteLine(reg2.Match(input).Value);//output &%
            }

            string input = "my phone number is 15861327445, please call me sometime.";
            Regex reg1 = new Regex(@"158\d{8}");//匹配以158为开头的11位手机号
            if (reg1.IsMatch(input))
            {
                Console.WriteLine(reg1.Match(input).Value);//output 15861327445
            }

            string input2 = "November is the 11 month of the year, you can use Nov for short.";
            Regex reg2 = new Regex(@"Nov(ember)?");//匹配Nov 或者November

            var matchs = reg2.Matches(input2);
            foreach (Match match in matchs)
            {
                Console.WriteLine(match.Value);//output November  Nov
            }

            string input3 = "1000, 100, 2003, 9999,10000";
            Regex reg3 = new Regex(@"\b[1-9]\d{3}\b");//匹配1000到9999的数字

            var matchs3 = reg3.Matches(input3);
            foreach (Match match in matchs3)
            {
                Console.WriteLine(match.Value);//output 1000 2003 9999  其中\b是指匹配单词的边界
            }

            string input4 = "1000, 100, 2003, 9999,10000,99,10,1, 99999";
            Regex reg4 = new Regex(@"\b[1-9][0-9]{2,4}\b");//匹配100到99999的数字

            var matchs4 = reg4.Matches(input4);
            foreach (Match match in matchs4)
            {
                Console.WriteLine(match.Value);//output 1000 100 2003 9999 10000 99999  其中\b是指匹配单词的边界
            }

            string input1 = "the color of shirt is gray and the color of shoes is grey too.";
            Regex reg1 = new Regex(@"^the");//匹配

            var matchs1 = reg1.Matches(input1);
            foreach (Match match in matchs1)
            {
                Console.WriteLine(string.Format("the value is:{0}; and the index is:{1}", match.Value, match.Index));//output the value is:the; and the index is:0
            }

            string input2 = "the color of shirt shirts is gray and the color of shoes is grey too.";
            Regex reg2 = new Regex(@"\b\w*irt\b");//匹配shirt单词,但不会匹配到shirts

            var matchs2 = reg2.Matches(input2);
            foreach (Match match in matchs2)
            {
                Console.WriteLine(string.Format("the value is:{0}; and the index is:{1}", match.Value, match.Index));//output the value is:shirt; and the index is:13
            }

            string input1 = "color: blue, grey, gray, white, black";
            Regex reg1 = new Regex(@"(grey)|(gray)");//匹配grey和gray

            var matchs1 = reg1.Matches(input1);
            foreach (Match match in matchs1)
            {
                Console.WriteLine(match.Value);//output grey, gray
            }

            string input1 = "2.5+1.5=4";
            Regex reg1 = new Regex(@"2\.5\+1\.5=4");//其中.和+在正则式中都是特殊字符，如果想匹配这些特殊字符本身的含义，那么在前面加上一个\

            var matchs1 = reg1.Matches(input1);
            foreach (Match match in matchs1)
            {
                Console.WriteLine(match.Value);//output 2.5+1.5=4
            }

            string input1 = "out of sight, out of mind";
            Regex reg1 = new Regex(@"(out of) sight, \1 mind");

            if (reg1.IsMatch(input1))
            {
                Console.WriteLine(reg1.Match(input1).Value);//output out of sight, out of mind
            }

            Console.WriteLine(reg1.Match(input1).Groups[1].Value);  // output out of

            string input2 = "out of sight, out of mind";
            Regex reg2 = new Regex(@"(?<Group1>out of) sight, \1 mind");

            if (reg2.IsMatch(input2))
            {
                Console.WriteLine(reg2.Match(input2).Value);//output out of sight, out of mind
            }
            Console.WriteLine(reg2.Match(input2).Groups["Group1"].Value);  // output out of

            string input3 = "out of sight, out out of mind mind";
            Regex reg3 = new Regex(@"(?<Group1>[a-z]+) \1");//匹配重复的单词

            if(reg3.IsMatch(input3))
            {
                Console.WriteLine(reg3.Replace(input3, "$1"));//output  out of sight, out of mind
                Console.WriteLine(reg3.Replace(input3, "${Group1}"));//output  out of sight, out of mind
            }

            string input4 = "out of sight, out of mind";
            Regex reg4 = new Regex(@"(?:out of) sight");//使用了非捕获?:后，在表达式内就不能使用\1去引用了

            if (reg4.IsMatch(input4))
            {
                Console.WriteLine(reg4.Match(input4).Groups[1].Value);  // output 空
            }        

            string input1 = "out of sight, out of mind";
            Regex reg1 = new Regex(@".* of");//默认贪婪模式，尽可能的匹配更多的文本。在遇到第一个of时，正则引擎并没有停止下来，继续执行以期望后面还有一个of，这样就可以匹配到更多的文本。如果后面没有匹配到新的of，刚执行回溯
            if (reg1.IsMatch(input1))
            {
                Console.WriteLine(reg1.Match(input1).Value);//output out of sight, out of
            }

            string input2 = "out of sight, out of mind";
            Regex reg2 = new Regex(@".*? of");//在指定重复次数的字符后面加上?,正则式则为非贪婪模式。一但遇到第一个符合条件的文本，就匹配结束
            if (reg2.IsMatch(input2))
            {
                Console.WriteLine(reg2.Match(input2).Value);//output out of
            }

            string input3 = "The title of cnblog is <h1>code changes the world</h1>";
            Regex reg3 = new Regex(@"<.+>");//贪婪模式:匹配HTML标记

            var matchs3 = reg3.Matches(input3);
            foreach (Match match in matchs3)
            {
                Console.WriteLine(match.Value);//output <h1>code changes the world</h1>
            }

            string input4 = "The title of cnblog is <h1>code changes the world</h1>";
            Regex reg4 = new Regex(@"<.+?>");//非贪婪模式:匹配HTML标记

            var matchs4 = reg4.Matches(input4);
            foreach (Match match in matchs4)
            {
                Console.WriteLine(match.Value);//output <h1> </h1>
            }

            string input1 = "Live for nothing, die for something,";
            Regex reg1 = new Regex(@"(.*)thing,");

            var matchs1 = reg1.Matches(input1);
            foreach (Match match in matchs1)
            {
                Console.WriteLine(match.Value);//output 
            }

            Regex reg2= new Regex(@"(?>.*)thing,");

            var matchs2 = reg2.Matches(input1);
            foreach (Match match in matchs2)
            {
                Console.WriteLine(match.Value);//output 
            }

            string input1 = "hello 1024 world 8080 bye";
            Regex reg1 = new Regex(@"\d{4}(?= world)");
            if (reg1.IsMatch(input1))
            {
                Console.WriteLine(reg1.Match(input1).Value);//output 1024
            }

            Regex reg2 = new Regex(@"\d{4}(?! world)");
            if (reg2.IsMatch(input1))
            {
                Console.WriteLine(reg2.Match(input1).Value);//output 8080
            }

            Regex reg3 = new Regex(@"(?<=world )\d{4}");
            if (reg3.IsMatch(input1))
            {
                Console.WriteLine(reg3.Match(input1).Value);//output 8080
            }


            Regex reg4 = new Regex(@"(?<!world )\d{4}");
            if (reg4.IsMatch(input1))
            {
                Console.WriteLine(reg4.Match(input1).Value);//output 1024
            }