Convert.ToUInt64 (String, Int32) converts string in a base to 64-bit unsigned integer.
Class Sample Public Shared Sub Main() Dim value As String = Convert.ToString(Long.MinValue, 16) Try Dim number As UInt64 = Convert.ToUInt64(value, 16) Console.WriteLine("0x{0} converts to {1}.", value, number) Catch e As OverflowException Console.WriteLine("Unable to convert '0x{0}' to an unsigned long integer.", _ value) End Try End Sub End Class