The .NET Framework is no longer new, but it continues to delight me with
the power it offers when developing solutions. A feature
that has garnered my attention is
WMI (Windows Management Instrumentation) services. Basically,
it provides the vehicle for interacting with the underlying
operating system (albeit Windows XP, Windows 2000, and so forth).
In previous incarnations of Windows development, I was forced to go
to the Windows API (Application Programming Interface) when such
functionality was needed, so WMI is a blessing.

Overview of WMI

WMI provides management functionality. It is
available on Windows XP and to a lesser degree on earlier Windows
versions. The System.Environment.dll file provides the WMI
functionality, so it must be added (as a reference) to a .NET
application when it is used. It also utilizes COM to work with the
underlying environment.

WMI providers wrap native Windows API code to
be utilized via WMI. The providers are utilized by the WMI object
manager. If you need to utilize the underlying native API, you work
with the WMI object manager via the
System.Environment namespace.

The .NET Framework includes a variety of
WMI providers to perform common tasks. Here is a small sampling
of these providers:

  • Active Directory Provider:
    allows access to the Active Directory. The first Windows platform
    to support it is 2000.
  • Configuration Provider:
    allows you to configure the .NET CLR (Common Language Runtime).
    This is included with the .NET Framework.
  • Disk Quota Provider: allows
    you to control disk quotas. The first Windows platform to support
    it is XP.
  • Event Log Provider: allows
    access to the Event Log. The first Windows platform to support it
    is NT.
  • Performance Counter
    Provider:     allows access to performance counters. The first
    Windows platform to support it is 2000.
  • System Registry Provider:
    allows access to the Registry. The first Windows platform to
    support it is NT.
  • Win32 Provider: allows
    access to environment variables. The first Windows platform to
    support it is 2000.

You may also create custom providers. WMI has
been included with the Windows operating system beginning with
Windows ME, but the available providers depend upon the Windows
version. Microsoft does offer the
WMI administrative tools, which allow you to see what is
available.

WMI in action

Now that you have a general idea of WMI and its
functionality, let’s examine taking advantage of it within your
.NET code. As previously stated, you must add a reference to the
System.Environment.dll to your project. In addition, you must
include the System.Environment namespace in your code (via the
Using statement in C#, import in J#, and Imports within VB.NET).
The following example accesses miscellaneous system properties:

using System;
using System.Management;
namespace Builder {
class WMIExample {
[STAThread]
static void Main(string[] args) {
try {
ManagementObject mo = new
ManagementObject(“Win32_ComputerSystem.Name=\”PENTIUM4\””);
Console.WriteLine(“Description: ” +
mo[“Description”].ToString());
Console.WriteLine(“Model: ” + mo[“Model”].ToString());
Console.WriteLine(“Number of processors: ” +
mo[“NumberOfProcessors”].ToString());
} catch (ManagementException e) {
Console.WriteLine(“Exception encountered: ” + e.ToString());
} catch (Exception e) {
Console.WriteLine(“Exception encountered: ” + e.ToString());
} } } }

Here’s the VB.NET equivalent:

Imports System.Management
Module Module1
Sub Main()
Try
Dim mo As ManagementObject
mo = New
ManagementObject(“Win32_ComputerSystem.Name=””PENTIUM4″””)
Console.WriteLine(“Description: ” +
mo(“Description”).ToString())
Console.WriteLine(“Model: ” + mo(“Model”).ToString())
Console.WriteLine(“Number of processors: ” +
mo(“NumberOfProcessors”).ToString())
Catch e As ManagementException
Console.WriteLine(“Management exception encountered: ” +
e.ToString())
Catch e As Exception
Console.WriteLine(“Exception encountered: ” + e.ToString())
End Try
End Sub
End Module

Let’s examine a few details of the code. First,
an instance of the ManagementObject class is used to work with WMI.
You can use a ManagementObject class to work with any object that’s
accessible via WMI. The WMI class
(Win32_ComputerSystem.Name=”Pentium”) is used to instantiate the
MangementObject object. You can use the previously mentioned WMI
administrative tools (WMI Object Browser) to discover the WMI
classes available on the target system. In addition to retrieving
information, you may alter values.

The next code sample changes the name assigned
to a hard drive:

using System;
using System.Management;
namespace Builder {
class WMIExample {
[STAThread]
static void Main(string[] args) {
try {
ManagementObject mo = new
ManagementObject(“Win32_LogicalDisk.DeviceID=\”F:\””);
mo.Get();
mo[“VolumeName”] = “FDrive”;
mo.Put();
} catch (ManagementException e) {
Console.WriteLine(“Exception encountered: ” + e.ToString());
} catch (Exception e) {
Console.WriteLine(“Exception encountered: ” + e.ToString());
} } } }

Here’s the VB.NET equivalent:

Imports System.Management
Module Module1
Sub Main()
Try
Dim mo As ManagementObject
mo = New
ManagementObject(“Win32_LogicalDisk.DeviceID=””F:”””)
mo.Get()
mo(“VolumeName”) = “New Volume”
mo.Put()
Catch e As ManagementException
Console.WriteLine(“Management exception encountered: ” +
e.ToString())
Catch e As Exception
Console.WriteLine(“Exception encountered: ” + e.ToString())
End Try
End Sub
End Module

This example is similar to the first one; the
difference is that the drive name property has changed. The get
method is called before making the change; it ensures the WMI
instance is correctly initialized with the current state of the
drive. After the new name has been assigned, the put method is
called to update the underlying object (note: be sure to save the
change).

The functionality is available when needed

WMI is an important aspect of the .NET
Framework that receives little attention. It allows you to interact
and manipulate various aspects of the environment in which the
application is running. In addition, you may use WMI to monitor
certain aspects of the environment such as changes to the system
via events.

TechRepublic’s free .NET newsletter, delivered each Wednesday, contains useful tips and coding examples on topics such as Web services, ASP.NET, ADO.NET, and Visual Studio .NET. Automatically sign up today!