Для точной строки:
Function ExistExactStringInArray(sourceArr() As String, searchedString As String, Optional ignoreCase As Boolean = True) As Boolean
Return (From element As String In sourceArr
Where CBool(If(ignoreCase, (
element?.Trim.ToLower = searchedString?.Trim.ToLower),
(element = searchedString)))).Count > 0
End Function
Для частичной строки:
Function ExistPartialStringInArray(sourceArr() As String, searchedString As String, Optional ignoreCase As Boolean = True) As Boolean
Return (From element As String In sourceArr
Where CBool(If(ignoreCase,
element?.Trim.ToLower.IndexOf(searchedString?.Trim.ToLower) > -1,
element.IndexOf(searchedString) > -1))).Count > 0
End Function