Regex - Get String Between / Get All Strings Betwen?

I can only seem to find help for PHP on this subject so am opening a new question!

I have written a function to get a string between 2 other strings but at the moment it is still returning the first part of the string and simply removing anything after the EndSearch value:

Public Function GetStringBetween(ByVal Haystack As String, ByVal StartSearch As String, ByVal EndSearch As String) As String
    If InStr(Haystack, StartSearch) < 1 Then Return False
    Dim rx As New Regex("(?=" & StartSearch & ").+(?=" & EndSearch & ")")
    Return (rx.Match(Haystack).Value)
End Function

Demo Usage:

Dim Haystack As String = "hello find me world"
    Dim StartSearch As String = "hello"
    Dim EndSearch As String = "world"
    Dim Content As String = GetStringBetween(Haystack, StartSearch, EndSearch)
    MessageBox.Show(Content)

Returns: hello find me

Also, in PHP I have the following function:

function get_all_strings_between($string, $start, $end){
preg_match_all( "/$start(.*)$end/U", $string, $match );
return $match[1];
}

Is there a similar function in VB.NET for preg_match_all?

Example Function (Non-Functional Due To Returning m.Groups):

Public Function GetStringBetween(ByVal Haystack As String, ByVal StartSearch As String, ByVal EndSearch As String, Optional ByVal Multiple As Boolean = False) As String
        Dim rx As New Regex(StartSearch & "(.+?)" & EndSearch)
        Dim m As Match = rx.Match(Haystack)
        I开发者_开发知识库f m.Success Then
            If Multiple = True Then
                Return m.Groups
            Else
                Return m.Groups(1).ToString()
            End If
        Else
            Return False
        End If
    End Function

I don't understand why you are using lookahead:

Dim rx As New Regex("(?=" & StartSearch & ").+(?=" & EndSearch & ")")

If StartSearch = hello and EndSearch = world, this generates:

(?=hello).+(?=world)

Which, matched against the string, finds and returns exactly what it's supposed to. Build something like:

Dim rx As New Regex(StartSearch & "(.+?)" & EndSearch)
Dim m As Match = rx.Match(Haystack)
If m.Success Then
    Return m.Groups(1).ToString()

' etc