Reading Windows Registry Carefully

In one of my projects, I recently ran into issues when adding a function to read a value from registry. This wasn’t a normal value and was meant to detect for use for testing. I had placed the functionality during the loading of the application and when testing in RAD Studio 10.4.2 Sydney, it worked great during debugging and testing out of the IDE in the Virtual Machine I use for development.

After some tracking, I realized it was in my code reading the registry and not using the proper calls or try/except protection.

I am just doing a read of the registry value, so different calls should be used to help overcome any user privileges issues.

First off, be sure you have System.Win.Registry in your uses clause.

Now lets set up a function to return the value of the registry.

function ReadRegistryValue: integer
const
  keyname = 'Software\Delphi.Rocks\MyApp';
  value = 'Testing123';
var
  Registry : TRegistry;
begin
  result := 0; // Default value of zero returned in case of an issue
  Registry := TRegistry.Create(KEY_READ); // Create the option with read only permissions
  try
    Registry.RootKey := HKEY_LOCAL_MACHINE; // Use the HKLM section
    // Check to make sure key even exists
    if Registry.KeyExists(keyname) then
    begin
      // Check to make sure value even exists
      if Registrly.ValueExists(value) then
      begin
          try
            result := Registry.ReadInteger(value); // Get the value from the DWord32 Registry entry
          except
            ShowMessage('There was a problem reading the registry');
          end;
      end;
    end;
  finally
    Registry.Free;
  end;
end;
  

Now with the new code, should the registry entry not be there, the application will get a zero value from the call and not cause any errors.