Entity Framework Core中批量插入考勤时自动赋值主表Id到子表

我在提交员工考勤数据时遇到问题：BulkAttendance模型的Id字段是数据库自动生成的（标记了[DatabaseGenerated(DatabaseGeneratedOption.Identity)]），需要把这个自动生成的Id值赋值给关联的BulkAttendanceDetail模型的AttendanceId字段。

模型类定义 #

public class BulkAttendance
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public int EmployeeCategoryId { get; set; }
    public int EmployeeLabourGroup {  get; set; }
    public int CompanyId { get; set; }
    public int BranchId { get; set; }
    public int FinancialYearId { get; set;}
    public int ApprovalStatus { get; set; }
    public int ApprovalLevel { get; set; }
    public DateTime? ApprovedDate { get; set; }
    public DateTime FromDate { get; set; }
    public DateTime ToDate { get; set; }
    public int UserId { get; set; }
    public int CurrencyPrecision { get; set; }
    public List<BulkAttendaceDetail> AttendanceDetail { get; set; }

}

public class BulkAttendaceDetail 
{
    public string AttendanceId { get; set; }
    public string FullName { get; set; }
    public DateTime DateWorked { get; set; }
    public DateTime LoginTime { get; set; }
    public DateTime LogoutTime { get; set; }
    public int Employeeid { get; set; }
    public int ProjectId { get; set; }
    public string ProjectName {  get; set; }
    public int Category { get; set; }
    public int WorkId { get; set; }
    public decimal Amount { get; set; }
    public int Work { get; set; }
    public decimal OverTime { get; set; }
    public decimal OverTimeAmount { get; set; }
    public string WorkCategoryName { get; set; }
    public string WorkShortName { get; set; }
    public decimal OvertimeRate { get; set; }
    public DateTime TimeIn { get; set; }
    public DateTime TimeOut { get; set; }
    public decimal SalaryAmount { get; set; }
}

当前插入数据的代码 #

public async Task BulkAttendanceEntry(List<BulkAttendance> attendances)
{
    try
    {
        foreach (var attendance in attendances)
        {
            await _bulkAttendanceContext.tbl_AttendanceMaster.AddAsync(attendance);

            if (attendance.AttendanceDetail != null && attendance.AttendanceDetail.Any())
            {
                foreach(var attendanceDetail in attendance.AttendanceDetail)
                {
                    
                }
            }
        }
    }
    catch(Exception)
    {
         throw;
    }
}

解决方案 #

核心问题是：调用AddAsync只是将实体加入EF Core上下文跟踪，此时数据库还未生成Id值，必须先调用SaveChangesAsync将BulkAttendance写入数据库，才能获取到自动生成的Id，之后再给关联的明细赋值并保存。

修改后的代码如下：

public async Task BulkAttendanceEntry(List<BulkAttendance> attendances)
{
    try
    {
        foreach (var attendance in attendances)
        {
            // 将主实体添加到上下文
            await _bulkAttendanceContext.tbl_AttendanceMaster.AddAsync(attendance);
            // 保存主实体以获取自动生成的Id
            await _bulkAttendanceContext.SaveChangesAsync();

            if (attendance.AttendanceDetail != null && attendance.AttendanceDetail.Any())
            {
                foreach(var attendanceDetail in attendance.AttendanceDetail)
                {
                    // 将主实体Id转为字符串赋值给明细的AttendanceId
                    attendanceDetail.AttendanceId = attendance.Id.ToString();
                    // 将明细实体加入上下文
                    _bulkAttendanceContext.tbl_AttendanceDetail.Add(attendanceDetail);
                }
                // 保存明细数据
                await _bulkAttendanceContext.SaveChangesAsync();
            }
        }
    }
    catch(Exception)
    {
         throw;
    }
}

补充说明

• 请将代码中的tbl_AttendanceDetail替换为你实际的BulkAttendaceDetail对应的DbSet名称。
• 也可以选择统一保存所有数据，先完成主实体的保存和明细的赋值，最后一次性提交：

public async Task BulkAttendanceEntry(List<BulkAttendance> attendances)
{
    try
    {
        foreach (var attendance in attendances)
        {
            await _bulkAttendanceContext.tbl_AttendanceMaster.AddAsync(attendance);
            await _bulkAttendanceContext.SaveChangesAsync();

            if (attendance.AttendanceDetail != null && attendance.AttendanceDetail.Any())
            {
                foreach(var attendanceDetail in attendance.AttendanceDetail)
                {
                    attendanceDetail.AttendanceId = attendance.Id.ToString();
                    _bulkAttendanceContext.tbl_AttendanceDetail.Add(attendanceDetail);
                }
            }
        }
        // 统一提交所有明细数据
        await _bulkAttendanceContext.SaveChangesAsync();
    }
    catch(Exception)
    {
         throw;
    }
}

内容的提问来源于stack exchange，提问作者user18243088