I am baffled what is going on here:

Dim sSearchIn As String = "Bla"

Dim sSearchFor As String = Vb6ChrW(65533) 'This results in the string "�"

Dim i As Integer = sSearchIn.IndexOf(sSearchFor, 0)

I expect "i" to be -1 because the string "�" does not exist in the string "Bla".

However, "i" is 0.

What am I missing?

Thank you!

Public Function Vb6ChrW(ByVal uKeyCode As Integer) As String

    Dim nChar As Char = Char.ConvertFromUtf32(uKeyCode)
    Return New String(nChar, 1)

End Function

CodePudding user response：

You are performing culture-sensitive search. It is behaving as documented:

In a culture-sensitive search, if value contains an ignorable character, the result is equivalent to searching with that character removed. If value consists only of one or more ignorable characters, the IndexOf(String, Int32) method always returns startIndex

If you wanted a char-code-level search, you should have used

sSearchIn.IndexOf(sSearchFor, StringComparison.Ordinal)

, that gives -1 as you expect.

You should also turn Option Strict On so that it correctly brakes your Vb6ChrW function that you don't need in the first place because ChrW exists.