user define function for vb.net windows application

Private Shared validData As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 @.-_"
Private Shared Function IsValid(c As Char) As Boolean
    Return validData.Contains(c)
End Function
Private Shared Function ContainsAllValid(s As String) As Boolean
	For Each c As Char In s
		If Not IsValid(c) Then
			Return False
		End If
	Next
	Return True
End Function