Question

我试图更好地理解课程，课程＆＃39;地址＆＃39;用作属性＆＃39; ShippingAddress＆＃39;中的类型。在班级＆＃39; Person＆＃39;，但我想知道如何为地址属性分配值，因为它在下面的方式给我一个错误：

上找到

**类型＆＃39; System.NullReferenceException＆＃39;的未处理异常发生在Classes_and_Objects.exe

中

附加信息：对象引用未设置为对象的实例。**

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;

    namespace Classes_and_Objects
    {
        class Program
        {
        static void Main(string[] args)
        {
            Person john = new Person();
            john.FirstName = "John";
            john.LastName = "Doe";
            john.ShippingAddress.StreetAddress = "78 Fake Street" ;
            john.ShippingAddress.City = "Queens";
            john.ShippingAddress.State = "NY";
            john.ShippingAddress.PostalCode = "345643";
            john.ShippingAddress.Country = "United States";
            }

        }

        public class Address
        {
            public string StreetAddress { get; set; }
            public string City { get; set; }
            public string State { get; set; }
            public string PostalCode { get; set; }
            public string Country { get; set; }
        }
        public class Person
        {
            public string FirstName { get; set; }
            public string LastName { get; set; }
            public Address ShippingAddress { get; set; }
        }

    }
    }

Answer 1

您还需要实例化地址。以下是编写代码的方法：

static void Main(string[] args)
{
    Person john = new Person();
    john.FirstName = "John";
    john.LastName = "Doe";
    john.ShippingAddress = new Address();
    john.ShippingAddress.StreetAddress = "78 Fake Street" ;
    john.ShippingAddress.City = "Queens";
    john.ShippingAddress.State = "NY";
    john.ShippingAddress.PostalCode = "345643";
    john.ShippingAddress.Country = "United States";
}

Answer 2

Jhon.shippingadress = new Address();

如何在另一个类中使用类作为属性，然后实例化它？ [C＃]

2 个答案: