Consistent method of extracting error code from exception

[wizofaus]

Currently I'm using this code:

        public static string? GetErrorCodeName(BaseError? error) =>
            ToErrorCodeName((error as SharePointRestError)?.ServerErrorCode ?? (error as CsomError)?.ServerErrorCode);

        static string? ToErrorCodeName(long? value) => value == null ? default :
            value == -2130575245 ? "InvalidFileOrFolderName" :
            value == -2147024809 ? "ListItemDeleted" :
            typeof(Microsoft.SharePoint.Client.ClientErrorCodes).GetFields(BindingFlags.Public | BindingFlags.Static)
                .FirstOrDefault(field => (int?)field.GetValue(null) == value)?.Name;

In order to get a meaningful error code from a ServiceError when thrown by PnP.Core or returned in batch results. Wondering if something like this could be included in PnP.Core, or whether there's a better way to do it? (what I'd really like to see is a well-defined enum!).
It seems a bit odd that ServerErrorCode is defined separately for SharePointRestError and CsomError given they mean the same thing and use the same values.

I'm not sure why -2130575245 or -2147024809 aren't part of Microsoft.SharePoint.Client.ClientErrorCodes - technically there is a separate value for "ListItemDeleted" when you get it via CSOM, but the error message is the same in both cases anyway. Actually I think -2147024809 is a more general error code that might just indicate a parameter is invalid, but in my case I'm only seeing it when trying to perform operations on deleted items.