VB.NET Ignore case match string

Public Sub FindText()
'大文字小文字区別して検索
If InStr("This is a book", "book") = 0 Then
MsgBox "No,match"
Else
MsgBox "find"
End If
End Sub

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Public Sub FindText()
'大文字小文字区別しない検索
If InStr(UCase("This is a Book"), UCase("book")) = 0 Then
MsgBox "No,match"
Else
MsgBox "find"
End If
End Sub