Regular expression (Regex class)

Namespaces:
System.Text.RegularExpressions

Initializing the Regex class
Regex regex = new Regex (regular expression, Regexoptions.ignorecase | Regexoptions.multiline);
IgnoreCase ignores case when matching, multiline adjusts the meaning of ^ and $ to match the beginning and end of a row.

Match () and Matches () methods:
Match () matches a result; matches () matches multiple results
Example: Fetching a row of consecutive digits from a string
Regex regex = new Regex (@ "/d+");
Match m = regex. Match ("bei2008jing@163.com");
Console.WriteLine (M.value.tostring ());
Output results:
2008

Extract all numbers from a section of string
Regex regex = new Regex (@ "/d+");
MatchCollection ms = Regex. Matches ("bei2008jing@163.com");
foreach (Match m in ms)
{
Console.WriteLine (M.value.tostring ());
}
Output results
2008
163

Split () function:
Single character segmentation
String str = "11123332444";
string[] array = str. Split (' 2 ');
foreach (string s in array)
{
Console.WriteLine (s);
}
Output results:
111
333
444

Multi-string Segmentation:
1.string str = "11122223332222444";
string[] Arrray = str. Split (New char[4]{' 2 ', ' 2 ', ' 2 ', ' 2 '});
foreach (string s in array)
{
Console.WriteLine (s);
}
Output results:
111

333

444

2.string str = "11122223332222444";
string[] array = regex.split (str, "2222", regexoption.ignorecase);
Regex regex = new Regex ("2222");
string[] Array = regex. Split (str);
foreach (string s in array)
{
Console.WriteLine (s);
}
Output results:
111
333
444

Batch string substitution:
String str = "11122223332222444";
Regex regex = new Regex ("2222");
str = regex. Replace (str, "a");
str = regex.replace (str, "2222", "a");
Console.WriteLine (str);
Console.ReadLine ();