Question

我想删除传真表中的传真和FaxData中与传真表中具有相同传真ID的记录我创建了viewmodel视图来连接2个表使用System.Web.Mvc;

namespace FaxProject.ViewModel
{
public class SendFaxVm
{

    public List<SelectListItem> Employees { set; get; }

    public int[] SelectedEmployees { set; get; }
    public Fax fax { set; get; }
    public int FaxId { set; get; }
    public string CompanyName { set; get; }
    public int Courier_Num { set; get; }
    public Nullable<int> NumberOfPages { get; set; }

    public string CompanyAddress { get; set; }
    public string ReceivingDate { get; set; }
    public string Attachment { get; set; }
    public string Subject { get; set; }

}
}

这是viewmodel

  public ActionResult Delete(int id,SendFaxVm vm,Fax fax)
    {
        foreach (var userId in vm.SelectedEmployees)
        {
            var faxdatadelete = Db.FaxDatas.Single(f => f.FaxId == fax.Id);
            Db.FaxDatas.Remove(faxdatadelete);

            Db.SaveChanges();
        }

        var deletedfax = Db.Faxes.Single(f => f.Id == id);
        Db.Faxes.Remove(deletedfax);
        Db.SaveChanges();






        return RedirectToAction("FaxForm", "Fax");
    }

这是传真控制器中的动作..... 这是我尝试删除时遇到的异常（在FaxProject.dll中发生了'System.NullReferenceException'类型的异常，但未在用户代码中处理

附加信息：未将对象引用设置为对象的实例。）

Answer 1

应该是：

public ActionResult Delete(int id, SendFaxVm vm, Fax fax)
{
    if (SendFaxVm == null || Fax == null)
    {
        return RedirectToAction("FaxForm", "Fax");
    }

    foreach (var userId in vm.SelectedEmployees)
    {
        var faxdatadelete = Db.FaxDatas.FirstOrDefault(f => f.FaxId == fax.Id);
        if (faxdatadelete != null)
        {
            Db.FaxDatas.Remove(faxdatadelete);
            Db.SaveChanges();
        }
    }

    var deletedfax = Db.Faxes.FirstOrDefault(f => f.Id == id);
    if (deletedfax != null)
    {
        Db.Faxes.Remove(deletedfax);
        Db.SaveChanges();
    }

    return RedirectToAction("FaxForm", "Fax");
}

如何从两个有关系的表中删除数据？

1 个答案: