如何解决异常错误？ [英] How to solve an exception error?

问题描述

我的控制器上面有上面的代码，

i have a above code on my controller,

public ActionResult Details(int? id)
{
   var dbo = new DrugBusiness();
   DrugModel dm = dbo.DetailsMethod(id);
   DateTime drug_expdate = dbo.GetAll().Find(x => x.DrugId == id).ExpiryDate;
   DateTime now = DateTime.Today;
   var days = drug_expdate - now;
   if(drug_expdate<=now)
   {
      ViewBag.msg = "The Drug has expired";
   }
   else
   {
      ViewBag.msg = "This Drug expires in " + days.Days + "Days";
   }
return PartialView(dbo.DetailsMethod(id));

但是当我运行我的详细信息视图时，它给出了一个黄色的错误，这就是

but when im running my Details view it's giving me an error in yellow line, this what

it says "{"Object reference not set to an instance of an object."}" 

请帮我试试但是什么都没有用，请

please help me ive try but nothing is working, please

推荐答案

你可能会注意到问号在 int？之后。这意味着id也可以为NULL，因此您必须检查它。

You might notice the questionmark after int?. This means that id can also be NULL so you have to check for that.

if(id.HasValue) {
  // do something
} else {
  // id is NULL, do something else
}

祝你好运！

Good luck!

你通过的身份证可能不是在记录中找到。因此，无法访问ExpiryDate。要么没有这样的id，要么你为id提供了一个空值。



您是否可以将可空的内容传递给方法。基于代码看起来它不是为处理这样​​的输入而设计的。

Probably the id you're passing cannot be found in records. Because of this, the ExpiryDate cannot be accessed. Either there is no such id or you have provided a null value for the id.

Is it intentional that you can pass a nullable into to the method. Based on the code it looks like it's not designed to handle such input.

在执行任何计算之前检查drug_expdate的值是否为空。

Check to see if the value for "drug_expdate is not null before performing any calculations.

DateTime drug_expdate = dbo.GetAll().Find(x => x.DrugId == id).ExpiryDate;
DateTime now = DateTime.Today;

if (drug_expdate != null)
{
    var days = drug_expdate - now;
}

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