C# Signature:

  [DllImport("iphlpapi.dll", ExactSpelling=true)]
    public static extern int SendARP( int DestIP, int SrcIP, byte[] pMacAddr, ref uint PhyAddrLen );

VB Signature:

Declare Function SendARP Lib "iphlpapi.dll" (ByVal DestIP As Integer _
    , ByVal SrcIP As Integer, ByVal pMacAddr As Byte(), ByRef PhyAddrLen As Integer) As Integer

User-Defined Types:

None.

Notes:

SendARP returns 0 on success. The parameter SrcIP can be 0.

Tips & Tricks:

Please add some!

The DestIP and SrcIP arguments should be UInt32 to avoid System.OverflowException when the last nibble of the IP-address is .128 or greater.

Sample Code:

This code help to get the MAC Address of a network card (You need to know the IP address)

Public Shared Function CreatePayload(ByVal IPAddress As String) As String
    Dim addr As IPAddress = IPAddress.Parse(indirizzo)
    Dim mac() As Byte = New Byte(6) {}
    Dim len As Integer = mac.Length
    SendARP(CType(addr.Address, Integer), 0, mac, len)
    Dim macAddress As String = BitConverter.ToString(mac, 0, len)
    Return macAddress
End Function

This is a similar C# sample

IPAddress dst = IPAddress.Parse("192.168.2.1"); // the destination IP address

byte[] macAddr = new byte[6];
uint macAddrLen = (uint)macAddr.Length;
if (SendARP((int)dst.Address, 0, macAddr, ref macAddrLen) != 0)
     throw new InvalidOperationException("SendARP failed.");

string[] str = new string[(int)macAddrLen];
for (int i=0; i<macAddrLen; i++)
     str[i] = macAddr[i].ToString("x2");

Console.WriteLine(string.Join(":", str));

Alternative Managed API:

Do you know one? Please contribute it!