RJCP.DeviceMgr

This library implements mechanisms to enumerate over the devices that are present in your Windows System. It uses Win32 API from CfgMgr32.dll which is available since Windows 2000. This code is highly compatible and is tested with Windows XP to Windows 11.

The current implementation provides readonly information. It is not designed that you can eject or modify the devices in the system.

It is called RJCP.IO.DeviceMgr, as it provides information very similar to when you manage your devices from the Windows Desktop and view the details of individual devices.

• 1. Testing
• 2. Using in Your Own Software
• 3. Implementation Details
  • 3.1. Win32 APIs used
    • 3.1.1. Getting a List of Devices
    • 3.1.2. Refreshing Devices
• 4. Known Issues
  • 4.1. Incomplete Set of Devices for GetList()
  • 4.2. No Phantom Devices with GetRoot().Refresh()
• 5. Release History
  • 5.1. Version 0.8.3
  • 5.2. Version 0.8.2
  • 5.3. Version 0.8.1
  • 5.4. Version 0.8.0

1. Testing

To quickly test the usage of the library, run the executable DeviceInfoDump. This gets the root tree node and dumps all information about the device tree to the console. This gives you an idea of the information that can be obtained.

2. Using in Your Own Software

Import the library into your project.

To set up logging, to see any errors or warnings, see Logging.md, and the example program DeviceInfoDump which is a minimal program for dumping information.

3. Implementation Details

3.1. Win32 APIs used

This implementation uses CfgMgr32.dll as described in the introduction. The APIs used are expected to be available for Windows XP and later.

3.1.1. Getting a List of Devices

Getting the list of all devices in the system uses the CM_Get_Device_ID_List API, which returns a list of all devices in the system, including those that are "phantom". No filter is applied when getting the list.

From the list of devices, CM_Locate_DevNode is used to get information about each device from the list returned, either "Normal" or "Phantom" devices. A tree of all devices is built after querying each device and getting information about the parent device in the tree.

The technique is described at MSDN

Using configuration manager functions:

1. Use CM_Get_Device_ID_List to retrieve a list of unique device instance identifier (ID) strings. To retrieve information only for devices that are present in the system, set CM_GETIDLIST_FILTER_PRESENT in the ulFlags parameter.

2. You can use the unique device instance ID with CM_Locate_DevNode to retrieve a DEVINST that represents the device to use with other configuration manager APIs.

3.1.2. Refreshing Devices

When refreshing devices, a different set of APIs are used. The root node is obtained with CM_Locate_DevNode, and then the tree is directly queried with CM_Get_Child and CM_Get_Sibling. These APIs only return devices that are active in the device tree.

4. Known Issues

4.1. Incomplete Set of Devices for GetList()

On some specific systems, the devices returned by DeviceInstance.GetList() is incomplete. Debugging shows that the list of strings returned by CM_Get_Device_ID_List is incomplete.

Calling a subsequent DeviceInstance.GetRoot().Refresh() removes any phantom devices, and can include extra devices that were previously not present, despite devices not being physically added by the user.

A workaround is to use DeviceInstance.GetRoot() instead of DeviceInstance.GetList() if no phantom devices are needed.

It is not intended to try and workaround this problem in software (by calling CM_Get_Device_ID_List and then enumerating the devices with CM_Get_Child and CM_Get_Sibling, trying to remember the phantom devices) due to potential race conditions.

This problem was observed in the case that an upgrade from Windows 10 to Windows 11 with SWD\PRINTENUM\{0C67E0C9-90A0-40EB-B1A6-470E41AB1CB7} and SWD\PRINTENUM\{C9730CC1-28FB-4572-A864-D9546A92F674} which have the friendly names OneNote and OneNote for Windows 10.

This was confirmed independently in a test program in C. See in docs/SampleCode.

4.2. No Phantom Devices with GetRoot().Refresh()

When using the API CM_Locate_DevNode to get the root node (even specifying CM_LOCATE_DEVNODE_PHANTOM on the root node), subsequent calls to CM_Get_Child and CM_Get_Sibling will not return phantom devices.

5. Release History

5.1. Version 0.8.3

Bug Fix:

• Don't refresh multiple times (DOTNET-1031)
• Fix refresh on device insertion (DOTNET-1033)

Quality:

• Clear cache on getting the list (DOTNET-1032)
• Don't use SafeDevInst and use IntPtr as there's nothing to free (DOTNET-1036)

5.2. Version 0.8.2

Do not use. Refresh doesn't work properly.

Quality:

• Reduce the amount of allocations on the heap (DOTNET-1021, #1)

5.3. Version 0.8.1

Quality:

• Add README.md to NuGet Package (DOTNET-813)
• Update from .NET 4.5 to .NET 4.6.2 (DOTNET-827)
• Update from .NET Standard 2.1 to .NET 6.0 (DOTNET-936, DOTNET-937, DOTNET-938, DOTNET-942, DOTNET-945)
• Update to .NET 8.0 (DOTNET-982, DOTNET-983, DOTNET-989, DOTNET-990)

5.4. Version 0.8.0

• Initial Release