An introduction to regular expressions (pattern matching)

This lesson covers the basics of pattern matching with regular expressions in VB.NET, with the aim of checking whether a string fits a fixed format.

A regular expression is a special notation describing the pattern of a string. Regex.Match() extracts the part that matches and Regex.IsMatch() tests whether it matches at all.

The sample code extracts something phone-number-shaped with Regex.Match() and tests whether "12345" is all digits with Regex.IsMatch(). The d stands for a single digit.

A common early stumble is remembering what the symbols mean. There are many of them — d, ^, $ — and picking up the common patterns first is the way in.

In professional work, regular expressions are used widely for validating and extracting text — checking the format of an email address or a phone number, pulling particular information out of a log file.

📖 Reference code

Dim text As String = "Phone: 090-1234-5678"
Dim m As Match = System.Text.RegularExpressions.Regex.Match(text, "\d{3}-\d{4}-\d{4}")
Console.WriteLine(m.Value)
Console.WriteLine(System.Text.RegularExpressions.Regex.IsMatch("12345", "^\d+$"))

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run VB.NET directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).