更新数据库 - 删除现有数据并使用 entityframework 添加新数据

Question

我的 StudentRegistration 模型 Class 如下

public partial class StudentRegistration
{
    public StudentRegistration()
    {            
        this.StudentReceipts = new HashSet<StudentReceipt>();            
    }

    public int Id { get; set; }
    public Nullable<int> StudentWalkInnID { get; set; } 
    ...
    ...  

    public virtual ICollection<StudentReceipt> StudentReceipts { get; set; }

}
public partial class StudentReceipt
{
    public int Id { get; set; }
    public Nullable<int> StudentRegistrationID { get; set; }
    ...
    ...    

    public virtual StudentRegistration StudentRegistration { get; set; }
}

我试图删除现有的学生收据列表并添加新的 list.The new studentreceipt list 正在正确添加到数据库中，但是 existing studentreceipt list 没有从数据库中删除并且 [= existing studentreceipt list 的 15=] 设置为 null。

我想从数据库中删除现有的 studentreceipt list 并添加新的 list.How 可以吗？

这是我试过的

using (TransactionScope _ts = new TransactionScope())
{
  _dbRegn = _db.StudentRegistrations
    .Where(r => r.Id == Id).FirstOrDefault();
  if (_dbRegn != null)
  {                      
    //Remove existing receipts
    foreach (var _existingReceipt in _dbRegn.StudentReceipts.ToList())
    {
      _dbRegn.StudentReceipts.Remove(_existingReceipt);
    }                           

    //adding new receipt
    foreach (var _receipt in mdlCourseInterchange.StudentReceiptList)
    {
      StudentReceipt _studReceipt = new StudentReceipt();
      //...
      //...
      _dbRegn.StudentReceipts.Add(_studReceipt);
    }
    //...
    //..

    db.Entry(_dbRegn).State = EntityState.Modified;
    int j = _db.SaveChanges();
    if (j > 0)
    {
      _ts.Complete();
      return Json(new { message = "success" }, JsonRequestBehavior.AllowGet);
    }
  }
}

Answer 1

您可以尝试下图

using (TransactionScope _ts = new TransactionScope())
{
  _dbRegn = _db.StudentRegistrations.Where(r => r.Id == Id).FirstOrDefault();

  if (_dbRegn != null)
  {                      
    //Remove existing receipts
    foreach (var _existingReceipt in _dbRegn.StudentReceipts.ToList())
    {
      __db.StudentReceipts.Remove(_existingReceipt);
    }                           

    //adding new receipt
    foreach (var _receipt in mdlCourseInterchange.StudentReceiptList)
    {
      StudentReceipt _studReceipt = new StudentReceipt();
      //...
      //...
      _db.StudentReceipts.Add(_studReceipt);
    }
    //...
    //..

    int j = _db.SaveChanges();
    if (j > 0)
    {
      _ts.Complete();
      return Json(new { message = "success" }, JsonRequestBehavior.AllowGet);
    }
  }
}

更新数据库 - 删除现有数据并使用 entityframework 添加新数据

Update Database - Deleting existing data and adding new data with entityframework

c#

entity-framework

asp.net-mvc-4

entity-framework-5