I am writing an application which detects if any bar-code scanner is attached to the pc or not. I don't know how to query the installed devices to check for barcode scanners. I am using C# and .NET 4.0.
Some barcode scanner are attached by keyboard wedge (Or their drivers report them as keyboards) - I believe there is no way to test if these are present.
Other specific scanners may be accessible through their USB ports but any status query will have to be on a model by model basis.