vb.net - case sensitive/insensitive search text in a string

Question

Hello,

I've been using text.indexof() to see if a string is located inside another string, however is it it possible to do a case sensitive/insensitive search option? I've been looking around Google and not having much luck with it.

A huge bonus would be if it could count the number of occurrences inside the string!

Answer 1

There are several overloads of IndexOf that take a StringComparison parameter, allowing you to specify the various culture and case-sensitivity options.

For example:

Dim idx As Integer = haystack.IndexOf(needle, StringComparison.OrdinalIgnoreCase)

As for counting occurrences, there's nothing built-in, but it's pretty straightforward to do it yourself:

Dim haystack As String = "The quick brown fox jumps over the lazy dog"
Dim needle As String = "th"
Dim comparison As StringComparison = StringComparison.OrdinalIgnoreCase

Dim count As Integer = CountOccurrences(haystack, needle, comparison)

' ...

Function CountOccurrences(ByVal haystack As String, ByVal needle As String, _
                          ByVal comparison As StringComparison) As Integer
    Dim count As Integer = 0
    Dim index As Integer = haystack.IndexOf(needle, comparison)
    While index >= 0
        count += 1
        index = haystack.IndexOf(needle, index + needle.Length, comparison)
    End While

    Return count
End Function