Neil Cowburn

I got an email last week asking about how to disable a particular network connection under Vista. The specific scenario, how to disable an active 3G connection, is not something I'm going to cover, but what I present below could be used as basis for that scenario.

With Vista, Microsoft introduced two new methods to the Win32_NetworkAdapter class under WMI: Enable and Disable. Before can call either of those methods, we need to know how to enumerate the network connections.

The .NET Framework SDK provides a helpful utility called mgmtclassgen.exe, which can be used to create .NET-friendly wrappers of the WMI classes. Open up a Visual Studio command prompt and enter the following:

mgmtclassgen Win32_NetworkAdapter -p NetworkAdapter.cs

This will generate a file called NetworkAdapter.cs which will contain a C# representation of the WMI Win32_NetworkAdapter class. You can add this source code file to your C# project and then access all the properties without too much extra effort.

To filter and disable the specific adapters, you do something like this:

SelectQuery query = new SelectQuery("Win32_NetworkAdapter", "NetConnectionStatus=2");
ManagementObjectSearcher search = new ManagementObjectSearcher(query);
foreach(ManagementObject result in search.Get())
{
    NetworkAdapter adapter = new NetworkAdapter(result);

    // Identify the adapter you wish to disable here. 
    // In particular, check the AdapterType and 
    // Description properties.

    // Here, we're selecting the LAN adapters.
    if (adapter.AdapterType.Equals("Ethernet 802.3")) 
    {
        adapter.Disable();
    }
}

Don't forget to add a reference to System.Management.dll!