Pattern matching in a textbox

I am trying to accomplish the following:

Read the contents of a textbox and look for a pattern match, then execute a series of events when (or if) that pattern is found.

That much I have accomplished, but how do I get the program to look for other instances of that pattern within the same textbox.

For instance, suppose the program finds a match at index 0 in the textbox, then executes its series of events. How do I get a recursion

of the text while ignoring the text section previously covered.

Imports SpeechLib

Imports System.Text.RegularExpressions

Public Class Form1

Dim compVoice As New SpVoice

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load

Dim regex As Regex = New Regex("^\d\d:\d\d")

Dim td As DateTime = DateTime.Now()

If CInt(TextBox1.Text) = td.Day Then

'run textbox1 here.

If regex.IsMatch(txtDay1.Text, 0) Then

compVoice.Volume = 100

compVoice.Speak("Warning")

compVoice.Volume = 50

compVoice.Speak(txtDay1.Text.Substring(6))

Else

compVoice.Speak("No text present.")

End If

ElseIf CInt(TextBox2.Text) = td.Day Then

'run textbox2 here

If regex.IsMatch(txtDay2.Text, 0) Then

compVoice.Volume = 100

compVoice.Speak("Warning")

compVoice.Volume = 50

compVoice.Speak(txtDay2.Text.Substring(6))

Else

compVoice.Speak("No text present.")

End If

ElseIf CInt(TextBox3.Text) = td.Day Then

If regex.IsMatch(txtDay3.Text, 0) Then

compVoice.Volume = 100

compVoice.Speak("Warning")

compVoice.Volume = 50

compVoice.Speak(txtDay3.Text.Substring(6))

Else

compVoice.Speak("No text present.")

End If

Else

Exit Sub

End If

End Sub

End Class

If you use the Regex.Match() method rather than Regex.IsMatch, then that returns a Match object rather than a Boolean. You can then test the Match object's Success property to see whether the Match was successful and, if it was, use its Index property to get the index of the first character in the match.

You can then call Regex.Match again with that index plus 5 to look for the next match, and so on. Notice that the Regex for subsequent searches will be slightly different as you won't need to include the '^' character (beginning of string) in the regular expression.

For more details and an example, check the documentation here:

http://msdn.microsoft.com/en-us/library/twcw2f1c.aspx

Notice that you can also use the Match object's NextMatch method to find the next match or get all matches at once with the Regex.Matches method. However, if the first match has to be at the beginning of the string, then they will be awkward to use because of the need to change the Regex after the first match. One thing you could do though would be to use "\d\d:\d\d" throughout and just check that the first match is at index 0.

1 Reply

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Vulpes13y ago
Accepted answer
If you use the Regex.Match() method rather than Regex.IsMatch, then that returns a Match object rather than a Boolean. You can then test the Match object's Success property to see whether the Match was successful and, if it was, use its Index property to get the index of the first character in the match.

You can then call Regex.Match again with that index plus 5 to look for the next match, and so on. Notice that the Regex for subsequent searches will be slightly different as you won't need to include the '^' character (beginning of string) in the regular expression.

For more details and an example, check the documentation here:

http://msdn.microsoft.com/en-us/library/twcw2f1c.aspx

Notice that you can also use the Match object's NextMatch method to find the next match or get all matches at once with the Regex.Matches method. However, if the first match has to be at the beginning of the string, then they will be awkward to use because of the need to change the Regex after the first match. One thing you could do though would be to use "\d\d:\d\d" throughout and just check that the first match is at index 0.
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