Delphi

hStatus := PdhOpenQuery(Nil, 0, hQuery);
if hStatus <> ERROR_SUCCESS then // hStatus = PDH_INVALID_ARGUMENT 
begin
  GetErrorMsg(hStatus, sErrorMsg); // sErrorMsg = 'argument is invalid or missing'
  Exit;
end;

implementaion
var

    PdhOpenQuery : function( pReserved: Pointer;
dwUserData: DWORD; phQuery: PDH_HQUERY  ): PDH_STATUS; stdcall;
// similarly the rest of the pdh functions here

DllHandle : THandle;
hStatus : PDH_STATUS;

procedure TClass.Create()
begin

DllHandle := LoadLibrary('pdh.dll');
if DllHandle <> 0 then
begin
  PdhOpenQuery := GetProcAddress( DllHandle, 'PdhOpenQuery' );
  // similarly the rest of the pdh functions here
end;

/////////////////////////////////////// storing this type based on 'StudentdId'
type TStudent = class
public
  StudentName, StudentClass : string;
  StudentId : Integer;
end;

///////////////////////////////////////// usage in other class like this

constructor TStudentClass.Create()
begin
m_objStudentList := TObjectDictionary<Integer, TStudent>.Create([doOwnsValues], 256);  // created TObjectDictionary object here.
end;

procedure TStudentClass.UpdateStudent(nId : Integer; sName : string);
var objStudent : TStudent;
begin
  objStudent := m_objStudentList.TryGetValue(nId, objStudent);
  if(objStudent = Nil) then Exit;

  objStudent.StudentName := sName;

  m_objStudentList.AddOrSetValue(nId, objStudent); // setting here. AFTER THIS, objStudent contains some weird values.

  // tried folloing as well but has same results
  //m_objStudentList.Items[nId] := objStudent;
end;

TServer = class (TOleServer)

private
  FOnEventEx : TNotifyEvent; // new one
  FOnEvent : TNotifyEvent;  // old one

published
  property OnEventEx : TNotifyEvent read FEventEx write FEventEx ; // new one
  property OnEvent: TNotifyEvent read FEvent write FEvent;  // old one

public
  procedure FireThisProc(); // This is the event I want to be fired ----------- based on new property 'OnEventEx'.
end; 

class function CoServer : IServer
begin
  MethodProp := GetMethodProp(TObject(TServer), 'OnEventEx');
  SetMethodProp(TObject(TServer) , 'OnEvent', MethodProp);

  Result := CreateComObject(CLASS_Server) as IServer;
end;