c#正则表达式——指定匹配位置

string pattern = @"^[a-z]w";//^后面的模式必须位于字符串的开始
            string input = "abc123efg456!nefg456";
            Regex regex = new Regex(pattern);
            var matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            regex = new Regex(pattern, RegexOptions.Multiline);//指定多行时多行生效
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }


            Console.WriteLine();
            pattern = @"[a-z][1-9]$";//$前面的模式必须位于字符串的末尾
            input = "abc123efg6nefg6";
            regex = new Regex(pattern);
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            regex = new Regex(pattern, RegexOptions.Multiline);//$多行也生效
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }


            Console.WriteLine();
            pattern = @"A[a-z]w";//A后面的模式必须位于字符串的开始处，而且忽略了多行标志
            input = "abc123efg456!nefg456";
            regex = new Regex(pattern);
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            regex = new Regex(pattern, RegexOptions.Multiline);//A后面的模式必须位于字符串的开始处，而且忽略了多行标志
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            pattern = @"[1-9]z";//z前面的模式必须位于字符串的末尾处，而且忽略了多行标志
            input = "abc123efg456nefg456n";
            regex = new Regex(pattern);
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            regex = new Regex(pattern, RegexOptions.Multiline);//z前面的模式必须位于字符串的末尾处，而且忽略了多行标志
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            pattern = @"[1-9]Z";//z前面的模式必须位于字符串的末尾处或者是字符串末尾n，而且忽略了多行标志
            input = "abc123efg456nefg456n";
            regex = new Regex(pattern);
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            regex = new Regex(pattern, RegexOptions.Multiline);//z前面的模式必须位于字符串的末尾处或者是字符串末尾n，而且忽略了多行标志
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }



            Console.WriteLine();
            pattern = @"[1-9]b";//匹配一个单词边界，这个边界就是单词字符和非单词字符的点，单词字符是[a-zA-Z0-9]中的任一字符，本模式指的是数字0到9后面必须是一个非单词
            input = "abc123efg456nefg456n";
            regex = new Regex(pattern);
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            regex = new Regex(pattern, RegexOptions.Multiline);//匹配一个单词边界，这个边界就是单词字符和非单词字符的点，单词字符是[a-zA-Z0-9]中的任一字符，和多行没有关系
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }



            Console.WriteLine();
            pattern = @"[1-9]B";//B和b是相反的，所以B肯定是单词与单词，非单词与非单词之间的点，本模式指的是数字0到9后面必须是一个单词
            input = "abc123efg456nefg456n";
            regex = new Regex(pattern);
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }

            Console.WriteLine();
            regex = new Regex(pattern, RegexOptions.Multiline);
            matchCollection = regex.Matches(input);
            foreach (Match item in matchCollection)
            {
                Console.WriteLine(item.Value == " " ? "空白" : item.Value);
            }