Question

有人可以帮助我解决我班上的问题吗？

我有一个地址类：

public class Address
{
    public string addressDescription { get; set; }
    public string addressNumber { get; set; }
    public string adddressLine1 { get; set; }
    public string adddressLine2 { get; set; }
    public string adddressLine3 { get; set; }
    public string addressPostCode { get; set; }
    public double addressLatitude { get; set; }
    public double addressLongitude { get; set; }
}

我有一个路线类：

public class Route
{
    public Address from { get; set; }
    public Address to { get; set; }
}

在我的控制器中，我设置了一些这样的虚拟信息：

public ActionResult FareCalculator(string from , string to)
    {

        var myroute = new Route();

        myroute.from.addressDescription = from;
        myroute.from.addressLatitude = 51.481581;
        myroute.from.addressLongitude = -3.179090;
        myroute.to.addressDescription = to;
        myroute.to.addressLatitude = 51.507335;
        myroute.to.addressLongitude = -0.127683;

        return View(myroute);
    }

但是当我运行项目时，它会落在myroute.from.addressDescription = from;表示对象引用未设置为对象的实例。

我看不出我做错了什么。有人可以帮忙吗？

由于

崔佛

Answer 1

您需要创建Address的新实例，并将其分配给from和to：

public ActionResult FareCalculator(string from , string to)
{

    var myroute = new Route();
    myroute.from = new Address(); // new instance
    myroute.from.addressDescription = from;
    myroute.from.addressLatitude = 51.481581;
    myroute.from.addressLongitude = -3.179090;

    myroute.to = new Address(); // new instance
    myroute.to.addressDescription = to;
    myroute.to.addressLatitude = 51.507335;
    myroute.to.addressLongitude = -0.127683;

    return View(myroute);
}

Answer 2

我可以建议使用构造函数初始化from和to字段吗？否则，每次使用Route类时都必须新建对象。

public class Route
{
    public Address from { get; set; }
    public Address to { get; set; }

    public Route()
    {
        from = new Address();
        to = new Address();
    }
}

这样您就可以使用您提供的代码：

    var myroute = new Route();

    myroute.from.addressDescription = from;
    myroute.from.addressLatitude = 51.481581;
    myroute.from.addressLongitude = -3.179090;
    myroute.to.addressDescription = to;
    myroute.to.addressLatitude = 51.507335;
    myroute.to.addressLongitude = -0.127683;

    return View(myroute);

Answer 3

您已创建Route个实例，但忘记创建Address的新实例（from和to）：

var myroute = new Route
{
    from = new Address(),
    to = new Address()
};

Answer 4

myroute.from和myroute.to应该是Address类的实例。

 public ActionResult FareCalculator(string from , string to)
 {
        var myroute = new Route();

        myroute.from = new Address();
        myroute.from.addressDescription = from;
        myroute.from.addressLatitude = 51.481581;
        myroute.from.addressLongitude = -3.179090;

        myroute.to = new Address();
        myroute.to.addressDescription = to;
        myroute.to.addressLatitude = 51.507335;
        myroute.to.addressLongitude = -0.127683;

        return View(myroute);
    }

C＃MVC类对象引用未设置为对象的实例

4 个答案: