Question

I am doing my homework for my visual basic class. I have most of the code written and everything seems to be working well except for my If Not statement that catches the exception when the loop does not find what it is looking for. Anyone see a problem with the way the code looks. The file is loaded in using the browse button already and it works find when I enter information that the loop can find.

Private Sub btnSearch_Click(ByVal sender As System.Object, ByVal e As   
System.EventArgs)

Handles btnSearch.Click
    'event level variables
    Dim Found As Boolean
    Dim Counter As Integer

    'looks for entry match
    If rdoAbbrev.Checked = True Then
        Do Until Found Or Counter > 257
            If Country(Counter).Abbreviation.ToUpper = txtAbbrev.Text.ToUpper Then
                Found = True
                txtCountry.Text = Country(Counter).Names
            Else
                Counter += 1
            End If
        Loop
    Else
        Do Until Found Or Counter > 257
            If Country(Counter).Names.ToUpper = txtCountry.Text.ToUpper Then
                Found = True
                txtAbbrev.Text = Country(Counter).Abbreviation
            Else
                Counter += 1
            End If
        Loop
        If Not Found Then
            MessageBox.Show("This is not a valid entry.", "NO MATCH FOUND", MessageBoxButtons.OK)
            If rdoAbbrev.Checked = True Then
                txtAbbrev.Text = ""
                txtAbbrev.Focus()
            Else
                txtCountry.Text = ""
                txtCountry.Focus()

            End If
        End If
    End If
    'match not found response

    'reset variables
    Counter = 0
    Found = False
End Sub

Answer 1

You If Not Found block only occurs if rdoAbbrev.Checked = True. Is that what you intended? If not, then that block of code should either be located outside of the first If block (below it) or you should have a second If block after the first While loop.

EDIT
It looks like Country is an array. You should probably use Counter >= Country.Length.

Arrays in VB.NET are 0-based. Meaning that the first item is located at Country(0), the second item is at Country(1), etc. If there are 100 elements in the array, then the last element is located at Country(99). Country(100) does not exist and will cause an Exception if you try to access it.

I’m not sure what the requirements of your homework are, but usually to iterate over the elements of a collection (array, list, etc), you would use a For loop. You can jettison from the loop early with the Exit command.

For Counter As Integer = 0 To Country.Length - 1
     '...Country(Counter)
     If Found Then Exit For
Next