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' CST1801 Visual Basic .NET

' Exercise 16.6 Number String solved using RegEx.

' Allen Benusa

' Apr 18, 2005


' This imports must be added by hand

Imports System.Text.RegularExpressions


Public Class frmMain

    Inherits System.Windows.Forms.Form


#Region " Windows Form Designer generated code "

#End Region


    Private Sub cmdCompute_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdCompute.Click

        Dim i As Integer

        Dim total As Integer = 0


        Dim sNumString As String = txtNumString.Text

        Dim numMatch As String = "[0-9]{1,7}"

        Dim opMatch As String = "\+|-"


        Dim mcnum As MatchCollection = Regex.Matches(sNumString, numMatch)

        Dim mcop As MatchCollection = Regex.Matches(sNumString, opMatch)


        ' Number of number groups needs to be one more than operators to be valid.

        If mcnum.Count = mcop.Count + 1 Then

            total = Convert.ToInt32(mcnum(0).ToString())

            For i = 1 To mcnum.Count - 1

                Dim number As Integer = Convert.ToInt32(mcnum(i).ToString())

                ' Apply the operator.

                If mcop(i - 1).ToString() = "+" Then total = total + number

                If mcop(i - 1).ToString() = "-" Then total = total - number

            Next


            lblResult.Text = Convert.ToString(total)

        Else

            lblResult.Text = "Invalid input"

        End If

    End Sub


    Private Sub txtNumString_Enter(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtNumString.Enter

        lblResult.Text = ""

    End Sub

End Class