//// custom codes public virtual async Task <string> GetNextChildCodeAsync(Guid?parentId) { var lastChild = await GetLastChildOrNullAsync(parentId); if (lastChild == null) { var parentCode = parentId != null ? await GetCodeAsync(parentId.Value) : null; return(SysFile.AppendCode(parentCode, SysFile.CreateCode(1))); } return(SysFile.CalculateNextCode(lastChild.Code)); }