Advanced Topics in Regular Expressions

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Page 567

LISTING 19.8: THE REPLACE ALL BUTTON'S CODE

Private Sub bttnReplace_Click(ByVal sender As System.Object, _
                              ByVal e As System.EventArgs) _
                              Handles bttnReplace.Click
    If chkRegEx.Checked Then
        Dim searchOptions As RegexOptions
        searchOptions = RegexOptions.Multiline
        If Not chkCase.Checked Then
                searchOptions = searchOptions Or RegexOptions.IgnoreCase
        End If
        RegEx = New System.Text.RegularExpressions.Regex( _
                         searchWord.Text, searchOptions)
        Dim selStart As Integer = EditorForm.txtBox.SelectionStart
        Dim replacementText As String
        replacementText = RegEx.Replace( _
                         EditorForm.txtBox.SelectedText, _
                         replaceWord.Text, _
                         System.Text.RegularExpressions._
                         RegexOptions.Multiline)
        EditorForm.txtBox.SelectedText = replacementText
        EditorForm.txtBox.Select(selStart, replacementText.Length)
        EditorForm.txtBox.ScrollToCaret()
    Else
        If EditorForm.txtBox.SelectedText <> '' " Then
            EditorForm.txtBox.SelectedText = replaceWord.Text
        End If
    End If
    bttnFindNext.PerformClick()
End Sub

You can experiment with the RegExEditor project, or even use it as a starting point for a highly specialized editor. Let's move on to some more advanced topics in regular expressions.

So far you've learned the basics of regular expressions. The metacharacters and symbols you've seen so far are adequate for many practical applications, but there are more topics to explore in regular expressions.

First, we'll examine the grouping of matches in a regular expression. A lengthy regular expression can be broken into simpler ones, which you can refer to later in the same regular expression. Being able to refer to previous matches allows you to perform very powerful searches (such as locating repeated words in a text).

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