This is the part 2 of the Exploring Delphi XE3 – WinApi Additions – Winapi.Functiondiscovery Article

One of the nice features of the Function Discovery API is the posibility of filter the results for device enumeration, for this you must use the CreateInstanceCollectionQuery method and then add the conditions for the query using the AddPropertyConstraint method.

Try this sample Delphi code which enumerates all the processors devices where the manufacturer is Intel.

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.Win.ComObj,
  Winapi.Windows,
  Winapi.Activex,
  Winapi.PropSys,
  Winapi.Functiondiscovery,
  System.SysUtils;

procedure Enumerate;
var
    LFunctionDiscovery : IFunctionDiscovery;
    LFunctionInstance  : IFunctionInstance;
    ppIFunctionInstanceCollection: IFunctionInstanceCollection;
    ppIFunctionInstanceCollectionQuery: IFunctionInstanceCollectionQuery;
    ppIPropertyStore  : IPropertyStore;
    pv : TPropVariant;
    pdwCount : DWORD;
    pszCategory: PWCHAR;
    hr : HResult;
    i : integer;
begin
  //create an instance to the  IFunctionDiscovery interface
  LFunctionDiscovery := CreateComObject(CLSID_FunctionDiscovery) as IFunctionDiscovery;
  try
    //set the provider to search
    pszCategory:=FCTN_CATEGORY_PNP;
    //get the devices collection
    hr := LFunctionDiscovery.CreateInstanceCollectionQuery(pszCategory, nil, false, nil, nil, ppIFunctionInstanceCollectionQuery);
      if Succeeded(hr)  then
      begin
       PropVariantClear(pv);
       pv.vt:=VT_LPWSTR;
       pv.pwszVal:='Intel';
       hr := ppIFunctionInstanceCollectionQuery.AddPropertyConstraint(PKEY_Device_Manufacturer, pv, QC_EQUALS);
       if not Succeeded(hr) then RaiseLastOSError;

       PropVariantClear(pv);
       pv.vt:=VT_LPWSTR;
       pv.pwszVal:='Processor';
       hr := ppIFunctionInstanceCollectionQuery.AddPropertyConstraint(PKEY_Device_Class, pv, QC_EQUALS);
       if not Succeeded(hr) then RaiseLastOSError;

        hr := ppIFunctionInstanceCollectionQuery.Execute(ppIFunctionInstanceCollection);
        if Succeeded(hr)  then
        begin
          //get the collection count
          ppIFunctionInstanceCollection.GetCount(pdwCount);
          if pdwCount=0 then
            Writeln(Format('No items was found for the %s category',[pszCategory]))
          else
          for i := 0 to pdwCount - 1 do begin
            //get the n Item of the collection
            if Succeeded(ppIFunctionInstanceCollection.Item(i, LFunctionInstance)) then
            begin
              //init the propertiess store
              LFunctionInstance.OpenPropertyStore(STGM_READ, ppIPropertyStore);
              //read the properties values
              if Succeeded(ppIPropertyStore.GetValue(PKEY_NAME, pv)) then
               Writeln(Format('Name          %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_InstanceId, pv)) then
               Writeln(Format('Instance Id   %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_Driver, pv)) then
               Writeln(Format('Device Driver %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_Model, pv)) then
               Writeln(Format('Model         %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_Manufacturer, pv)) then
               Writeln(Format('Manufacturer  %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_LocationInfo, pv)) then
               Writeln(Format('Location      %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_Class, pv)) then
               Writeln(Format('Class        %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_ClassGuid, pv)) then
               Writeln(Format('Class Guid   %s',[pv.puuid^.ToString]));
              Writeln;
            end
            else
             RaiseLastOSError;
           end;
        end;
      end
      else
       RaiseLastOSError;
  finally
    LFunctionDiscovery:=nil;
  end;
end;

begin
 try
   ReportMemoryLeaksOnShutdown:=True;
   if (Win32MajorVersion >= 6) then  // available on Vista (or later)
   begin
    if Succeeded(CoInitializeEx(nil, COINIT_MULTITHREADED)) then
    try
     Enumerate;
    finally
      CoUninitialize;
    end;
   end
   else
   Writeln('Windows version not compatible');
 except
    on E:Exception do
        Writeln(E.Classname, ':', E.Message);
 end;
 Writeln('Press Enter to exit');
 Readln;
end.