Developing a page with asp.net (vb) and I am getting an error using an .IndexOfAny when I use a string but when just characters it works fine

My code is:
VB Code:
  1. Dim sPhrase as String
  2. Dim sList() as String = {" AND ", "OR"}
  3. sPhrase = "John AND Mary"
  4.  
  5. lblPhrase.Text = sPhrase
  6.  
  7. If sPhrase.IndexOfAny(sList) = 0 Then
  8.   lblResult.Text = "Not Found"
  9. Else
  10.   lblResult.Text = "Found"
  11. End If

The following gives the following error:
BC30332: Value of type '1-dimensional array of String' cannot be converted to '1-dimensional array of Char' because 'String' is not derived from 'Char'.

If I change the following line:
Dim sList() as String = {" AND ", "OR"}

to

Dim sList() as Char = {"a", "e"}

Things seem to work fine. Is it not possible to search and array of strings with the IndexOfAny?

Thanks.