Convert.ToInt64 (String, Int32) converts string in a base to a 64-bit signed integer.
Module Example Public Sub Main() Dim value As String = ULong.MaxValue.ToString("X") Try Dim number As Long = Convert.ToInt64(value, 16) Console.WriteLine("0x{0} converts to {1}.", value, number) Catch e As OverflowException Console.WriteLine("Unable to convert '0x{0}' to a long integer.", value) End Try End Sub End Module