Hi Coconet ,

As I know, DHCP doesn't support WMI interface for query, we'd better use
DHCP API to query these information. However, I did not find any C# or .Net
code for this task yet. Below is the detailed C++ code using DHCP API to
obtain these information, you have to perform p/invoke to use it in C#:

// sss.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include "stdafx.h"
#include <windows.h>
#include "Winsock2.h"
#include <dhcpsapi.h> /* Please link dhcpsapi.lib to the project. */

DWORD
DhcpDottedStringToIpAddress(
LPSTR String
)
/*++

Routine Description:
This functions converts a dotted decimal form ASCII string to a
Host order IP address.

Arguments:
String - The address to convert.

Return Value:
The corresponding IP address.

--*/
{
struct in_addr addr;

addr.s_addr = inet_addr( String );
return( ntohl(*(LPDWORD)&addr) );
}

LPSTR
DhcpIpAddressToDottedString(
DWORD IpAddress
)
/*++

Routine Description:

This functions converts a Host order IP address to a dotted decimal
form ASCII string.

Arguments:

IpAddress - Host order IP Address.

Return Value:

String for IP Address.

--*/
{
DWORD NetworkOrderIpAddress;

NetworkOrderIpAddress = htonl(IpAddress);
return(inet_ntoa( *(struct in_addr *)&NetworkOrderIpAddress));
}

int main(int argc, char *argv[])
{
DWORD dwMajor, dwMinor;
DWORD nRet;
LPDHCP_CLIENT_INFO_ARRAY clinfo;
DWORD subnet_ip;
char subnet_ip1[128];
DHCP_RESUME_HANDLE handle = NULL;
DWORD read = 0, total = 0;

if(argc <2)
{
printf (" Please input the DHCP server IP \n");
printf (" for example: sss.exe 192.168.1.1 \n");
return 0;
}

WCHAR GlobalServerIpAddressUnicodeString[256];

MultiByteToWideChar( CP_ACP, 0, argv[1],
strlen(argv[1])+1, GlobalServerIpAddressUnicodeString,

sizeof(GlobalServerIpAddressUnicodeString)/sizeof(GlobalServerIpAddressUnico
deString
[0]) );

nRet = DhcpGetVersion(GlobalServerIpAddressUnicodeString, &dwMajor,
&dwMinor);
if ( nRet == ERROR_SUCCESS )
{
}
else
{
printf("\nDhcpGetVersion() error = %d", nRet);
return 1;
}
/* The argv[1] must be Unicode string that specifies the IP address of the
DHCP
server. */

DWORD dwError = ERROR_MORE_DATA;
DWORD dwElementsRead = 0, dwElementsTotal = 0;
LPDHCP_IP_ARRAY pdhcpIpArray = NULL;
DWORD m_dwPreferredMax = 0xFFFFFFFF;
DHCP_RESUME_HANDLE m_dhcpResumeHandle = NULL;
SYSTEMTIME SystemTime;
FILETIME LocalTime;
//
// for this server, enumerate all of it's subnets
//
while (dwError == ERROR_MORE_DATA)
{
dwError = DhcpEnumSubnets(GlobalServerIpAddressUnicodeString,
&m_dhcpResumeHandle,
m_dwPreferredMax,
&pdhcpIpArray,
&dwElementsRead,
&dwElementsTotal);

if (dwElementsRead && dwElementsTotal && pdhcpIpArray)
{
//
// loop through all of the subnets that were returned
//
for (DWORD i = 0; i < pdhcpIpArray->NumElements; i++)
{

//printf("DHCP Subnet number = %d\n", pdhcpIpArray->NumElements);

strcpy (subnet_ip1, DhcpIpAddressToDottedString(pdhcpIpArray->Elements[i]));
subnet_ip = pdhcpIpArray->Elements[i];
//printf("DHCP Subnet IP address = %s\n",
DhcpIpAddressToDottedString(subnet_ip));

nRet = DhcpEnumSubnetClients(GlobalServerIpAddressUnicodeString, subnet_ip,
&handle, 0xFFFFFFFF, &clinfo, &read, &total);
if ( (nRet == ERROR_MORE_DATA ) || (nRet == ERROR_SUCCESS) )
{
for (DWORD j=0; j< clinfo->NumElements; j++)
{
wprintf(L"clients name= %s", clinfo->Clients[j]->ClientName);
printf("\tIP= %s \t Subnet IP address=%s\n",
DhcpIpAddressToDottedString(clinfo->Clients[j]->ClientIpAddress),subnet_ip1)
;

printf("\tExpires = ");

FileTimeToLocalFileTime((FILETIME
*)(&clinfo->Clients[j]->ClientLeaseExpires),
&LocalTime) ;
FileTimeToSystemTime( &LocalTime, &SystemTime );

printf( "%02u/%02u/%02u %02u:%02u:%02u.\n",
SystemTime.wMonth,
SystemTime.wDay,
SystemTime.wYear,
SystemTime.wHour,
SystemTime.wMinute,
SystemTime.wSecond );

}
}
else
{
printf("\nDhcpEnumSubnetClients() error = %d", nRet);
}

} //for

} // if

} ///while
return 0;
}

Thanks and Merry Christmas!

Best regards,
Jeffrey Tan
Microsoft Online Community Support
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Hi Coconet ,

Have you reviewed my reply to you? Does it make sense to you? If you still
need any help, please feel free to feedback, thanks.

Best regards,
Jeffrey Tan
Microsoft Online Community Support