創建一個整數參數，其值僅在0 - 3之間

Question

我想僅使用數字0 - 3之間的整數參數，我該怎麼做？

我用枚舉試過，但它不允許的起始編號是這樣

Public Enum Octet_Num As Integer 
    0 
    1 
    2 
    3 
End Enum 

下面的代碼將工作的一個整數，但它似乎不練的好編碼標準？

Public Enum Octet_Num 
    first_octet 
    second_octet 
    third_octet 
    fourth_octet 
End Enum 

Function Get_Octet_IPAdd(octet_num As Usage_Get_Octet_IPAdd) 

Dim octet As Integer 

If octet_num = Octet_Num.first_octet Then 
    Octet = 0 
End If 

If octet_num = Octet_Num.second_octet Then 
    Octet = 1 
End If 

If octet_num = Octet_Num.third_octet Then 
    Octet = 2 
End If 

If octet_num = Octet_Num.fourth_octet Then 
    Octet = 3 
End If 

Dim fourthOctet As String = Format(IPAddress.Parse("192.168.1.130").GetAddressBytes(3), "000") 
    Return fourthOctet 
End Function 

Answer 1

枚舉是整數類型，並且可以在.GetAddressBytes(index)

Public Enum OctetNum 
    First = 0 
    Second = 1 
    Third = 2 
    Fourth = 3 
End Enum 

Function Get_Octet_IPAdd(octet_num As OctetNum) 

    Return Format(IPAddress.Parse("192.168.1.130").GetAddressBytes(octet_num), "000") 

End Function