Working With Devices: Actually getting to the devices

Up to this point we've worked with Device Classes. We now should get into the actual devices. Devices are grouped into Device Information Sets. If I understand Microsoft's description of it, Devices are grouped by Device Setup and Device Interface Classes. As mentioned previously Setup Classes are things like Network Adapters, while Interface Classes are things like PCI connections. These groupings can be pulled by using the SetupDiGetClassDevs function.

Private Declare Auto Function SetupDiGetClassDevs Lib "Setupapi.dll" (ByRef ClassGuid As Guid, ByVal Enumerator As UInt32, ByVal hwndParent As IntPtr, ByVal Flags As UInt32) As IntPtr

Out of the four arguments, I am only going to use the first and last. The first argument is the Guid that I want to retrieve. The Guid(s) we retrieved from the SetupDiClassGuidsFromNames can be used here. I think that Device Interface Class Guids could be used as well, I just never had a need for it.

The second argument are the flags we will use. The enumeration is defined below. You can refer to the function definition as to which one you want to use. You probably want to experiment with these to see which one suits your needs. I think that Present and Profile are your best bets if you are unsure.

'Scope to retrieve devices
Public Enum DeviceInfoSet_Scope
DIGCF_DEFAULT = &H1
DIGCF_PRESENT = &H2
DIGCF_ALLCLASSES = &H4
DIGCF_PROFILE = &H8
DIGCF_DEVICEINTERFACE = &H10
End Enum

Here is our code.

'Returns a Device Info Set based on Class Guid
Private Function GetDeviceInfoSet(ByVal ClassGuid As Guid, ByVal Scope As DeviceInfoSet_Scope) As IntPtr
Dim Result As IntPtr = SetupDiGetClassDevs(ClassGuid, Convert.ToUInt32(0), IntPtr.Zero, Convert.ToUInt32(Scope))
Return Result
End Function

Our result is returned as an IntPtr variable type.

It is important to note that once you are done with this object you need to destroy it. You can use the SetupDiDestroyDeviceInfoList to destory the IntPtr's. Here is the definition along with the code.

Private Declare Auto Function SetupDiDestroyDeviceInfoList Lib "Setupapi.dll" (ByVal DeviceInfoSet As IntPtr) As Boolean

'Destroys the device Info set
Public Sub DestroyDeviceInfoSet(ByVal DevInfoSet As IntPtr)
SetupDiDestroyDeviceInfoList(DevInfoSet)
End Sub

So the end result is a pointer to an object that will contain a list of devices.