pinvoke.net: Edit: iphlpapi.SendARP

@msdn=http://msdn.microsoft.com/en-us/library/windows/desktop/aa366358(v=vs.85).aspx
@pinvoke=http://pinvoke.net/$$$.htm

Summary: Send ARP message to a Network Card in the LAN
!!!!C# Signature:
  [DllImport("iphlpapi.dll", ExactSpelling=true)]
  public static extern int SendARP( 
      uint DestIP, uint SrcIP, byte[] pMacAddr, ref int PhyAddrLen);

!!!!VB Signature:
  Declare Function SendARP Lib "iphlpapi.dll" (
      ByVal DestIP As UInt32, ByVal SrcIP As UInt32, _
      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 GetMAC(ByVal IPAddress A

Dim addr As IPAddress = IPAddress.Parse(IPAddress)
        Dim mac() As Byte = New Byte(6) {}
        Dim len As Integer = mac.Length
        SendARP(CType(addr.Address, UInt32), 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(
 
 // Please do not use the IPAddress.Address property
 // This API is now obsolete. --> http://msdn.microsoft.com/en-us/library/system.net.ipaddress.address.aspx
 // to get the IP in Integer mode use

uint uintAddress = BitConverter.ToUInt32(dst.GetAddressBytes(), 0);
 byte[] macAddr = new byte[6];
 int macAddrLen = macAddr.Length;
 int retValue = SendARP(uintAddress, 0, macAddr, ref macAddrLen);
 if (retValue != 0) {
    throw new Win32Exception(retValue, "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!

Documentation: SendARP@msdn on MSDN

in vb: because of "Public Overloads Property Address As Long. This property has been deprecated." Hope this is helpful for someone!

Public Shared Function GetMAC(ByVal IPAddresse As String) As String

Dim macAddress = ""
        Dim dst As IPAddress = Net.IPAddress.Parse(IPAddresse)
        Dim uintAddress = BitConverter.ToUInt32(dst.GetAddressBytes(), 0)
        Dim macAddr() As Byte = New Byte(6) {}
        Dim macAddrLen As Integer = macAddr.Length
        Dim retValue = SendARP(uintAddress, 0, macAddr, macAddrLen)
        Dim str(macAddrLen) ' = New String(macAddrLen).ToString
        For i = 0 To macAddrLen - 1
             macAddress = macAddress & macAddr(i).ToString("x2") & ":"
        Next
        macAddress = Mid(macAddress, 1, Len(macAddress) - 1)
        Return macAddress
    End Function