c#正则表达式——替换

 string pattern = "(mr|dr) ([A-Z])[a-z]*";
            string str = "mr Jhons$,dr Tom$";
            Regex regex = new Regex(pattern);

            var ouputStr = regex.Replace(str, "Mr X");
            Console.WriteLine(ouputStr);

            Console.WriteLine();
            ouputStr = regex.Replace(str, "$1 X");//$group，使用group指定的组号
            Console.WriteLine(ouputStr);

            Console.WriteLine();
            ouputStr = regex.Replace(str, "$2 X");//$group，使用group指定的组号
            Console.WriteLine(ouputStr);

            Console.WriteLine();
            ouputStr = regex.Replace(str, "$+ X");//把找到的匹配使用最后一个组替换
            Console.WriteLine(ouputStr);

         
            

            Console.WriteLine();
            pattern = "(?mr|dr) ([A-Z])[a-z]*";
            regex = new Regex(pattern);
            ouputStr = regex.Replace(str, "${groupName} X");//把找到的所有匹配使用groupName替换
            Console.WriteLine(ouputStr);


            Console.WriteLine();
            pattern = "mr [A-Z][a-z]*";
            str = "mr Jhons!";
            regex = new Regex(pattern);
            ouputStr = regex.Replace(str, "$");//把找到的匹配使用$替换
            Console.WriteLine(ouputStr);

            Console.WriteLine();
            pattern = "mr [A-Z][a-z]*";
            str = "@!mr Jhons";
            regex = new Regex(pattern);
            ouputStr = regex.Replace(str, "$`");//把找到的匹配使用匹配前的文本去替换，在这里匹配前的文本是"@!"。
            Console.WriteLine(ouputStr);

            Console.WriteLine();
            pattern = "mr [A-Z][a-z]*";
            str = "%mr Jhons@!";
            regex = new Regex(pattern);
            ouputStr = regex.Replace(str, "$'");//把找到的匹配使用匹配后的文本去替换，在这里匹配后的文本是"@!"。
            Console.WriteLine(ouputStr);

            Console.WriteLine();
            pattern = "mr [A-Z][a-z]*";
            str = "%mr Jhons@!";
            regex = new Regex(pattern);
            ouputStr = regex.Replace(str, "$_");//把找到的匹配使用整个的字符串，也就是str的值来替换
            Console.WriteLine(ouputStr);