private static string AddTasks(TeisterMaskContext context, Project project, TaskImportDTO[] tasks)
        {
            StringBuilder result = new StringBuilder();

            foreach (var taskDto in tasks)
            {
                if (IsValid(taskDto) &&
                    IsValidOpenDate(taskDto.OpenDate, project.OpenDate) &&
                    IsValidDueDate(taskDto.DueDate, project.DueDate))
                {
                    Task task = new Task
                    {
                        Name          = taskDto.Name,
                        OpenDate      = DateTime.ParseExact(taskDto.OpenDate, "dd/MM/yyyy", CultureInfo.InvariantCulture),
                        DueDate       = DateTime.ParseExact(taskDto.DueDate, "dd/MM/yyyy", CultureInfo.InvariantCulture),
                        ExecutionType = (ExecutionType)taskDto.ExcecutionType,
                        LabelType     = (LabelType)taskDto.LabelType,
                        Project       = project
                    };

                    context.Add(task);
                }
                else
                {
                    result.AppendLine(ErrorMessage);
                }
            }

            context.SaveChanges();

            return(result.ToString().TrimEnd());
        }