$ 表示其前面的字符必须位于字符串的结束处
/b 匹配一个单词的边界
/B 匹配一个非单词的边界
另外，还包括：/A 前面的字符必须位于字符处的开始处，/z 前面的字符必须位于字符串的结束处，/Z 前面的字符必须位于字符串的结束处，或者位于换行符前
下面提供一些简单的示例：
string i = "Live for nothing,die for something";
Regex r = new Regex("^Live for nothing,die for something$");
//r.IsMatch(i) true
Regex r = new Regex("^Live for nothing,die for some$");
//r.IsMatch(i) false
Regex r = new Regex("^Live for nothing,die for some");
//r.IsMatch(i) true
string i = @"Live for nothing,
die for something";//多行
Regex r = new Regex("^Live for nothing,die for something$");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,die for something$", RegexOptions.Multiline);
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,/r/ndie for something$");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,$");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,$", RegexOptions.Multiline);
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,/r/n$");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,/r/n$", RegexOptions.Multiline);
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,/r$");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,/r$", RegexOptions.Multiline);
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^die for something$");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^die for something$", RegexOptions.Multiline);
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("$");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^", RegexOptions.Multiline);
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("$", RegexOptions.Multiline);
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex("^Live for nothing,/r$/n^die for something$", RegexOptions.Multiline);
Console.WriteLine("r match count:" + r.Matches(i).Count);//
//对于一个多行字符串，在设置了Multiline选项之后，^和$将出现多次匹配。
string i = "Live for nothing,die for something";
string m = "Live for nothing,die for some thing";
Regex r = new Regex(@"/bthing/b");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex(@"thing/b");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
Regex r = new Regex(@"/bthing/b");
Console.WriteLine("r match count:" + r.Matches(m).Count);//
Regex r = new Regex(@"/bfor something/b");
Console.WriteLine("r match count:" + r.Matches(i).Count);//
///b通常用于约束一个完整的单词
