可以把符合條件取代

string s1 = s

Rgex r = new Regex  //宣告 ?變數名稱 用$

s1 = r.Rex

pattern="<tr>(.*)

--------------------------------------

// Declare object variable of type Regex.
    Regex r;
    // Create a Regex object and define its regular expression.
    r = new Regex("\s2000");

Regex r = new Regex("abc"); 
    Match m = r.Match("123abc456");
    if (m.Success)
    {
        Console.WriteLine("Found match at position " + m.Index);
    }
------------------

MatchCollection mc;
    String[] results = new String[20];
    int[] matchposition = new int[20];
    
    Regex r = new Regex("abc"); 
    mc = r.Matches("123abc4abcd");
    for (int i = 0; i < mc.Count; i++)
    {
        results[i] = mc[i].Value;
        matchposition[i] = mc[i].Index;  
    }

----------------------------------------------

using System;
using System.Text.RegularExpressions;

    public class RegexTest
    {
        public static void RunTest()
        {
            Regex r = new Regex("(a(b))c");
            Match m = r.Match("abdabc");
            Console.WriteLine("Number of groups found = " + m.Groups.Count);
        }
        public static void Main()
        {
            RunTest();
        }
    }

output: Number of groups found = 3
----------------------------------------------------------------------------------------------

using System;
    using System.Text.RegularExpressions;

    public class RegexTest
        {
        public static void RunTest()
        {
            int counter;
            Match m;
            CaptureCollection cc;
            GroupCollection gc;

            Regex r = new Regex("(Abc)+"); 
            m = r.Match("XYZAbcAbcAbcXYZAbcAb");
            gc = m.Groups;

            Console.WriteLine("Captured groups = " + gc.Count.ToString());

            for (int i=0; i < gc.Count; i++)
            {
                cc = gc[i].Captures;
                counter = cc.Count;
                
                Console.WriteLine("Captures count = " + counter.ToString());
                
                for (int ii = 0; ii < counter; ii++)
                {
                    Console.WriteLine(cc[ii] + "   Starts at character " +
                        cc[ii].Index);
                }
            }
        }

        public static void Main() {
            RunTest();
        }
    }

http://phorum.study-area.org/viewtopic.php?t=25450&highlight=regular+expression