Using C# to Query WMI

Using WMI

In addition to the Registry, there’s another source available to you for obtaining IP network information from Windows systems. The Windows Management Instrumentation (WMI) is the Microsoft implementation of Web-Based Enterprise Management (WBEM), which is a standard for accessing system information in a network environment, developed by the Distributed Management Task Force, Inc. (DMTF). Since Windows 2000, Microsoft has included in the OS a database that contains information regarding system hardware and software, as well as current hardware status. The C# language can query the database to determine the status of managed hardware and software components, including network devices.

IP Info in WMI

The WMI Win32 NetworkAdapterConfiguration table within WMI contains information related to the network devices installed on the system. The result of the table query is a collection of information for each network interface. Each network interface represents one record in the returned collection. The IP information for the network interface appears as separate fields within the record.

Using C# to Query WMI

The .NET System.Management namespace contains classes used for querying the WMI databases. You can create a C# program to query WMI for each network interface installed on the system and then display the IP information returned. The steps to use to query the WMI database from a C# program are as follows:

1. Create a ManagementObjectSearcher object that contains a SQL Select statement for the database table.
2. Create a ManagementObjectCollection object to obtain the result set from executing the SQL query.
3. In a foreach loop, assign a new ManagementObject for each object in the Management-ObjectCollection.
4. Assign the desired data fields to regular type variables.

Listing 2.3 shows the WMICardGrab.cs program, which uses the C# WMI classes to obtain the network interface IP information.

Listing 2.3: WMICardGrab.cs program

using System;
using System.Management;
class WMICardGrab
{
  public static void Main ()
  {
    ManagementObjectSearcher query = new
    ManagementObjectSearcher("SELECT * FROM Â
     Win32_NetworkAdapterConfiguration WHERE IPEnabled = 'TRUE'");
    ManagementObjectCollection queryCollection = query.Get();
    foreach( ManagementObject mo in queryCollection )
    {
      string[] addresses = (string[])mo["IPAddress"];
      string[] subnets = (string[])mo["IPSubnet"];
      string[] defaultgateways =
           (string[])mo["DefaultIPGateway"];
      Console.WriteLine("Network Card: {0}",
             mo["Description"]);
      Console.WriteLine("  MAC Address: {0}",
             mo["MACAddress"]);
      foreach(string ipaddress in addresses)
      {
        Console.WriteLine("  IP Address: {0}",
             ipaddress);
      }
      foreach(string subnet in subnets)
      {
        Console.WriteLine("  Subnet Mask: {0}", subnet);
      }
      foreach(string defaultgateway in defaultgateways)
      {
        Console.WriteLine("  Gateway: {0}",
             defaultgateway);
      }
    }
  }
}

The C# WMI class ManagementObjectSearcher defines the SQL query that will be performed against the WMI database. You can use the IPEnabled field to your advantage, filtering out any network devices that do not have IP configured:

ManagementObjectSearcher query = new
    ManagementObjectSearcher("SELECT * FROM Â
    Win32_NetworkAdapterConfiguration WHERE IPEnabled = 'TRUE'");
ManagementObjectCollection queryCollection = query.Get();

The result of the query is stored in a ManagementObjectCollection. Each collection item represents one record in the result set, and each record represents one network interface. The handy foreach C# function can be used to iterate through the retrieved recordset collection, examining each record individually and assigning it to a ManagementObject object. Fields within the record are referenced using their proper field name:

string[] addresses = (string[])mo["IPAddress"];
string[] subnets = (string[])mo["IPSubnet"];
string[] defaultgateways = (string[])mo["DefaultIPGateway"];

Similar to the Registry version, the IPAddress, IPSubnet, and DefaultIPGateway values are arrays that can contain more than one value. To accommodate this, you must assign the result to a string array, and step through the string array, again with a foreach statement.

The IP information retrieved from the WMICardGrab program should be the same as from the Registry version:

C:\>WMICardGrab
Network Card: D-Link DE660 PCMCIA LAN adapter
  MAC Address: 00:80:C8:BC:CE:C3
  IP Address: 192.168.1.6
  Subnet Mask: 255.255.255.0
  Gateway: 192.168.1.1
C:\>

Using DNS

The last way to determine system IP information is to utilize the C# DNS (Domain Name System) classes. 

The C# System.Net namespace contains the Dns class, which comprises several methods that allow you to obtain DNS information about hosts. The GetHostName() method retrieves the hostname of the local system. The GetHostByName() method attempts to find the IP address of a hostname. You can combine these two functions to find the IP address of the local system. 

Listing 2.4: DNSName.cs program

using System;
using System.Net;
class DNSName
{
  public static void Main ()
  {
   string hostName = Dns.GetHostName();
   Console.WriteLine("Local hostname: {0}", hostName);
   IPHostEntry myself = Dns.GetHostByName(hostName);
   foreach (IPAddress address in myself.AddressList)
   {
   Console.WriteLine("IP Address: {0}", address.ToString());
   }
  }
}

Again, similar to the Registry and WMI programs, you must take into account the possibility of the local system having more than one IP address assigned to it. The AddressList property of the IPHostEntry class is an array of type IPAddress. You can use the foreach function to extract each of the IP addresses in the array. The output of this program is very simple:

C:\>DNSName
Local hostname: abednego
IP Address: 192.168.1.6
C:\>

This is a very common method to use to get the local system IP address for determining the local IP address to use for creating server network connections.