Why doesn't my Delphi function get my comm ports from the registry?

Question

My code:

procedure EnumCommPorts(aStrings: TStrings);
var
  Registry: TRegistry;
begin
  Registry := TRegistry.Create;
  try
    Registry.RootKey := HKEY_LOCAL_MACHINE;
    Registry.OpenKey('hardware\devicemap\serialcomm', False);
    Registry.GetKeyNames(aStrings);
  finally
    Registry.Free;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  EnumCommPorts(Memo1.Lines);
end;

The screenshot below shows that there are 2 comm ports defined:

However, when I click the button Memo1 remains empty. How do I fix this?

Answer 1

You have a couple of mistakes.

First of all you are attempting to open the registry with write access. You won't get that as a standard user, with UAC enabled, under HKLM.

And secondly you call GetKeyNames by mistake. That returns the names of all sub-keys. The SERIALCOMM node has no sub-keys. Just so that you are clear, the DEVICEMAP node has five sub-keys, one of which is SERIALCOMM. You need to call GetValueNames.

This code will work:

Registry.RootKey := HKEY_LOCAL_MACHINE;
Registry.OpenKeyReadOnly('hardware\devicemap\serialcomm');
Registry.GetValueNames(aStrings);