无法检查数组是否为空

Question

我在asp.net mvc应用程序中有folloiwng动作方法: -

 public ActionResult CustomersDetails(long[] SelectRight)
        {

            if (SelectRight == null)
            {
                ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists see your system administrator.");
                RedirectToAction("Index");
            }
            else
            {
                var selectedCustomers = new SelectedCustomers
                {
                    Info = SelectRight.Select(GetAccount)
                };




                return View(selectedCustomers);
            }
            return View();
        }

但是如果它SelectRight Array是空的,那么它将绕过if (SelectRight == null)检查,它将呈现CustomerDetails视图并在视图内的以下代码上引发异常

@foreach (var item in Model.Info) {
    <tr>

那么如何使空检查工作正常呢？

Answer 1

你必须返回结果RedirectToAction(..).

 public ActionResult CustomersDetails(long[] SelectRight)
 {
      if (SelectRight == null)
      {
           ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists see your system administrator.");
           return RedirectToAction("Index");
      }
      else
      {
           '...

Answer 2

您可以将条件更改为以下条件:

...
if (SelectRight == null || SelectRight.Length == 0)
...

这应该有所帮助.

编辑

关于上面代码的重要注意事项是在c#中,或者运算符||是短路的.它看到数组为null(语句为true)并且不会尝试计算第二个语句(SelectRight.Length == 0),因此不会抛出NPE.