How is regex used in C#?

In C#, Regex (regular expression) is a class used for handling string matching and replacement. It provides a powerful and flexible way to search, match, and manipulate text data.

Here are some common methods and uses of Regex:

1. Check if the input string contains content that matches the pattern, and return a boolean value.
2. Regex.Match(string input, string pattern): Search for the first string in the input string that matches the pattern and return a Match object containing the results.
3. Regex.Matches(string input, string pattern): Searches the input string for all matches with the pattern, and returns a MatchCollection object that contains all the matching results.
4. The Regex.Replace method searches for content within the input string that matches the specified pattern and replaces it with the specified replacement string.
5. The method Regex.Split(string input, string pattern) is used to split the input string based on a specified pattern and return an array of strings.
6. The special characters and syntax used in regular expressions, such as . (matches any character except for a newline), * (matches 0 or more times), + (matches 1 or more times), ? (matches 0 or 1 time), \d (matches a digit character), etc.

Original: 我希望你很快就好起来。
Paraphrased: I hope you recover quickly.

string input = "Hello, my name is John. I live in New York.";
string pattern = @"\b\w{4}\b"; // 匹配长度为4的单词

bool isMatch = Regex.IsMatch(input, pattern);
Match match = Regex.Match(input, pattern);
MatchCollection matches = Regex.Matches(input, pattern);
string replaced = Regex.Replace(input, pattern, "****");
string[] splitted = Regex.Split(input, @"\W+"); // 根据非单词字符进行分割

Console.WriteLine(isMatch); // 输出：True
Console.WriteLine(match.Value); // 输出：name
foreach (Match m in matches)
{
    Console.WriteLine(m.Value); // 输出：name, John, live
}
Console.WriteLine(replaced); // 输出：Hello, my **** is ****. I **** in **** ****.
foreach (string s in splitted)
{
    Console.WriteLine(s); // 输出：Hello, my, name, is, John, I, live, in, New, York
}

This is just one use case of the Regex class, there are many other functions and options available. Regex allows for more advanced and complex string matching and manipulation.