Detailed explanation of C regular expression Regex common matching

Using the Regex class requires a reference to the namespace: using System. Text. RegularExpressions;

1. Authentication with the Regex class

Example 1: The annotated code serves the same purpose, except that one is a static method and one is an instance method

var source = " What did Liu Bei, Guan Yu, Zhang Fei and Sun Quan ask ";
//Regex regex = new Regex(" Sun Quan ");
//if (regex.IsMatch(source))
//{
// Console.WriteLine(" String contains sensitive words : Sun Quan! ");
//}
if (Regex.IsMatch(source, " Sun Quan ")) 
{
 　　 Console.WriteLine(" String contains sensitive words : Sun Quan! ");
}
Console.ReadLine();

Example 2: Using a constructor with two parameters, the second parameter indicates ignoring case, which is very common

var source = "123abc345DEf";
Regex regex = new Regex("def",RegexOptions.IgnoreCase);
if (regex.IsMatch(source))
{
 　　 Console.WriteLine(" String contains sensitive words :def ! ");
} 
Console.ReadLine();

2. Replace with the Regex class
Example 1: Simple case

var source = "123abc456ABC789";
//  Static method 
//var newSource=Regex.Replace(source,"abc","|",RegexOptions.IgnoreCase);
//  Instance method 
Regex regex = new Regex("abc", RegexOptions.IgnoreCase);
var newSource = regex.Replace(source, "|");
Console.WriteLine(" Original string: "+source);
Console.WriteLine(" Replaced string: " + newSource);
Console.ReadLine();

Results:

Original String: 123abc456ABC789

Replaced string: 123456789

Example 2: Replace the matching option with the html code, we use the MatchEvaluator delegate

var source = "123abc456ABCD789"; 
Regex regex = new Regex("[A-Z]{3}", RegexOptions.IgnoreCase);
var newSource = regex.Replace(source,new MatchEvaluator(OutPutMatch));
Console.WriteLine(" Original string: "+source);
Console.WriteLine(" Replaced string: " + newSource);
Console.ReadLine();

 // Soft City 

private static string OutPutMatch(Match match)
{
 　　 return "<b>" +match.Value+ "</b>";
}

Output:

Original String: 123abc456ABCD789

Replaced string: 123 < b > abc < /b > 456 < b > ABC < /b > D789

3. C # Regular Expression Regex Common Matches

#region  ID card number regular expression 
      // He asked 
      
        Console.WriteLine(" Please enter 1 ID number ");
        string id = Console.ReadLine();
        bool b4 = Regex.IsMatch(id, @"^\d{15}|\d{18}$");
        bool b5 = Regex.IsMatch(id, @"^(\d{15}|\d{18})$");
        Console.WriteLine(b4);
        Console.WriteLine(b5);
      
      #endregion

      #region  Match phone number 
      //hovertree
      

        Console.WriteLine(" Please enter a phone number ");
        string phone = Console.ReadLine();
        bool b = Regex.IsMatch(phone, @"^((\d{3,4}\-\d?{7,8})|(\d{5}))$");
        Console.WriteLine(b);
      
      #endregion

      #region  Matching email Adj. regex

      //hovertree
      
        Console.WriteLine(" Please enter Email Address ");
        string email = Console.ReadLine();
        bool bhvt = Regex.IsMatch(email, @"^\w+@\w+\.\w+$");
        Console.WriteLine(bhvt);
      
      #endregion

      #region  Matching ip Address regex
      //hovertree
      
        Console.WriteLine(" Please enter 1 A IP Address ");
        string ip = Console.ReadLine();
        bool bkly = Regex.IsMatch(ip, @"^\d{1,3}(\.\d{1,3}){3}$");
        Console.WriteLine(bkly);
      
      #endregion

      #region  Matching date is legal regex
      // He asked 
      
        Console.WriteLine(" Please enter 1 Date ");
        string date = Console.ReadLine();
        bool bhovertree = Regex.IsMatch(date, @"^\d{4}\-\d{1,2}\-\d{1,2}$");
        Console.WriteLine(bhovertree);
      
      #endregion


      #region  Matching url Address regex
      //"http://hovertree.com"
      //"http://keleyi.com/a/bjae/h1o76nuh.htm?id=3&name=aaa"
      //"https://s.taobao.com/search?q=hover+tree&js=1&stats_click=search_radio_all%3A1&initiative_id=staobaoz_20151204&ie=utf8"
      //"ftp://127.0.0.1/myslider.txt"

      //hovertree
      
        Console.WriteLine(" Please enter url Address ");
        string url = Console.ReadLine();
        bool bkeleyi = Regex.IsMatch(url, @"^[a-zA-Z]+://.+$");
        Console.WriteLine(bkeleyi);
      
      #endregion

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