Visual Basic .NET Find a Word

From Regex Regular Expression Encyclopedia

You can use this recipe for finding single words in a block of text. The expression will find only complete words surrounded by spaces or other word delimiters, such as punctuation or the beginning or end of a line.

code

Imports System
Imports System.IO
Imports System.Text.RegularExpressions
Public Class Recipe
    Private Shared _Regex As Regex = New Regex("\bsomething\b")
    Public Sub Run(ByVal fileName As String)
        Dim line As String
        Dim lineNbr As Integer = 0
        Dim sr As StreamReader = File.OpenText(fileName)
        line = sr.ReadLine
        While Not line Is Nothing
            lineNbr = lineNbr + 1
            If _Regex.IsMatch(line) Then
                Console.WriteLine("Found match '{0}' at line {1}", _
                    line, _
                    lineNbr)
            End If
            line = sr.ReadLine
        End While
        sr.Close()
    End Sub
    Public Shared Sub Main(ByVal args As String())
        Dim r As Recipe = New Recipe
        r.Run(args(0))
    End Sub
End Class

How It Works

A special character class, \b, allows you to easily search for whole words. This is an advantage because without doing a whole bunch of extra work you can make sure that a search for some- thing, for example, doesn’t yield unexpected matches such as somethings. You can break the regular expression shown here into the following:

This expression differs just slightly from the C# and Visual Basic .NET examples because the RegularExpressionValidator control assumes that the expression is to match the entire value (there’s an implied ^ at the beginning of the expression and $ at the end of the expres- sion). The combination .* has been added before and after the word boundary \b so the full word can float around inside the line.