Using regular expressions in Visual Basic .NET can be accomplished using the System.Text.RegularExpressions namespace. This namespace provides classes for compiling and executing regular expressions, as well as tools for pattern matching and substitution.
Here's an example of how to use regex in Visual Basic .NET:
``vb.net
Imports System.Text.RegularExpressions
Module Module1
Sub Main()
Dim input As String = "The quick brown fox jumps over the lazy dog"
Dim pattern As String = "\b\w{4}\b" 'matches 4-letter words
Dim matches As MatchCollection = Regex.Matches(input, pattern)
For Each match As Match In matches
Console.WriteLine(match.Value) 'prints "quick", "brown", "jumps", "over", "lazy"
Next
End Sub
End Module
`
In this example, we import the System.Text.RegularExpressions namespace and define a String variable input with our text. We then define a String variable pattern that will match 4-letter words using the \b character to match word boundaries and \w to match word character symbols.
We then use the Regex.Matches method to execute the regular expression pattern pattern on the input string input and retrieve all matches as a MatchCollection. The MatchCollection contains a collection of Match objects, each representing a match found in the input string.
Finally, we iterate over the MatchCollection using a For Each loop and print the matched words using the Match.Value` property.