Question

private void Right_Click(object sender, EventArgs e)
{         
   using (var ctx = new NORTHWNDEntities())
   {
       if (currentIndex < ctx.Employees.Count())
       {
           currentIndex++;
           Employee empl = ctx.Employees.ToList().ElementAt(currentIndex);


           Id.Text = empl.EmployeeID.ToString();
           FirstName.Text = empl.FirstName;
           LastName.Text = empl.LastName;
           DateOfBirth.Text = empl.BirthDate.Value.ToShortDateString();
       }
       else
       {
           Load();
       }
   }
}

所以我必须遍历这个集合，但是当我到达集合的末尾时，我得到了这个异常。有人能告诉我为什么我的if块不能阻止那种异常吗？感谢

Answer 1

在数组访问后移动增量。您遇到异常，因为您正在尝试访问不属于为阵列分配的内存的内存。

private void Right_Click(object sender, EventArgs e)
{         
    using (var ctx = new NORTHWNDEntities())
    {


        if (currentIndex < ctx.Employees.Count())
        {
            Employee empl = ctx.Employees.ToList().ElementAt(currentIndex);


            Id.Text = empl.EmployeeID.ToString();
            FirstName.Text = empl.FirstName;
            LastName.Text = empl.LastName;
            DateOfBirth.Text = empl.BirthDate.Value.ToShortDateString();
            currentIndex++;
        }
        else
        {
            Load();
        }
    }

}

Answer 2

执行currentIndex++;

在Employee empl = ctx.Employees.ToList().ElementAt(currentIndex);

之后

＆＃39; System.ArgumentOutOfRangeException＆＃39;

2 个答案: