如何在具有多个类的 Json 中修复反序列化<对象引用中的空>

Question

我能够反序列化根对象，但无法访问底层类，我收到空引用异常。我需要从订单类中提取字段。

在以下方案中，反序列化 效果很好，可以提取附加到项目的字段

var  Sresponse = JsonConvert.DeserializeObject<RootObject>(json);
Console.WriteLine(Sresponse.items);

但是在这里不起作用

var  Sresponse = JsonConvert.DeserializeObject<Item>(json);
Console.WriteLine(Sresponse.orderitems);

错误消息： 系统.空引用异常： 对象引用未设置为对象的实例

请帮忙。

Json String 
{
"totalcount": 103952,
"items": [
{
"orderid": 113951,
"email": "",
"namefirst": "",
"namelast": "",
"company": "",
"moneyfinal_net": "95.92",
"moneyfinal_vat": "23.98",
"moneytotal_gross_roundoff": "0.00",
"moneytotal_gross_all": "119.90",
"checkouttypename": "Card",
"deliverytypename": "",
"orderdate": 1554836745,
"orderstateid": 10,
"paymentstateid": 20,
"ordertypeid": 10,
"registerid": "{AD16AEE2-235F-318A-4323-6B63EC2C40E7}",
"warehouseid": 18,
"datereserved": null,
"currencycode": "NOK",
"additionaldata": {
"pos-timezone": "Europe/Oslo",
"pos-staff-externalid": "4654"
},
"orderitems": [
{
"orderitemid": 0,
"orderitemtype": 10,
"productid": 5486,
"productname": "Test",
"sku": "320991800016",
"productattributes": "",
"externalinput": "",
"externalinputtitle": "",
"unitlabel": "ST",
"quantity": 1,
"decimalunitquantity": null,
"moneynetpriceperunit": "63.92",
"moneypriceorg": "0.00",
"vatvalue": 25,
"deliveryinfo": "",
"moneyitemtotal_net": "63.92",
"moneyitemtotal_vat": "15.98",
"voucherid": 0,
"vouchercode": "",
"vouchername": "",
"moneyoriginalprice": "63.92",
"moneydiscountedprice": "0.00",
"moneydiscount": "0.00",
"salestaxes": [],
"additionaldata": {},
"decimalquantitytotal": "1.000",
"moneynetpriceperquantity": "63.92"
},

Classes 
public class Orderitem
{
public int orderitemid { get; set; }
public int orderitemtype { get; set; }
public int productid { get; set; }
public string productname { get; set; }
public string sku { get; set; }
public string productattributes { get; set; }
public string externalinput { get; set; }
public string externalinputtitle { get; set; }
public string unitlabel { get; set; }
public int quantity { get; set; }
public object decimalunitquantity { get; set; }
public string moneynetpriceperunit { get; set; }
public string moneypriceorg { get; set; }
public int vatvalue { get; set; }
public string deliveryinfo { get; set; }
public string moneyitemtotal_net { get; set; }
public string moneyitemtotal_vat { get; set; }
public int voucherid { get; set; }
public string vouchercode { get; set; }
public string vouchername { get; set; }
public string moneyoriginalprice { get; set; }
public string moneydiscountedprice { get; set; }
public string moneydiscount { get; set; }
public List<object> salestaxes { get; set; }
public string decimalquantitytotal { get; set; }
public string moneynetpriceperquantity { get; set; }
}
public class Item
{
public int orderid { get; set; }
public string moneyfinal_net { get; set; }
public string checkouttypename { get; set; }
public int orderdate { get; set; }
public int orderstateid { get; set; }
public string registerid { get; set; }
public int warehouseid { get; set; }
public string currencycode { get; set; }
public List<Orderitem>  orderitems { get; set; }

public class RootObject
{
public int totalcount { get; set; }
public List<Item> items { get; set; }
}

Answer 1

首先，在修复问题中错误定义的 JSON 字符串之后，然后在您的案例中使用此Model结构：

注意：要解析 JSON 中具有特殊字符(如-)Property名称，您可以使用如下所示的JSONProperty属性来解析这些属性。

public class Additionaldata
{
[JsonProperty(PropertyName = "pos-timezone")]
public string postimezone { get; set; }
[JsonProperty(PropertyName = "pos-staff-externalid")]
public string posstaffexternalid { get; set; }
}
public class Orderitem
{
public int orderitemid { get; set; }
public int orderitemtype { get; set; }
public int productid { get; set; }
public string productname { get; set; }
public string sku { get; set; }
public string productattributes { get; set; }
public string externalinput { get; set; }
public string externalinputtitle { get; set; }
public string unitlabel { get; set; }
public int quantity { get; set; }
public object decimalunitquantity { get; set; }
public string moneynetpriceperunit { get; set; }
public string moneypriceorg { get; set; }
public int vatvalue { get; set; }
public string deliveryinfo { get; set; }
public string moneyitemtotal_net { get; set; }
public string moneyitemtotal_vat { get; set; }
public int voucherid { get; set; }
public string vouchercode { get; set; }
public string vouchername { get; set; }
public string moneyoriginalprice { get; set; }
public string moneydiscountedprice { get; set; }
public string moneydiscount { get; set; }
public List<object> salestaxes { get; set; }
public Additionaldata additionaldata { get; set; }
public string decimalquantitytotal { get; set; }
public string moneynetpriceperquantity { get; set; }
}
public class Item
{
public int orderid { get; set; }
public string email { get; set; }
public string namefirst { get; set; }
public string namelast { get; set; }
public string company { get; set; }
public string moneyfinal_net { get; set; }
public string moneyfinal_vat { get; set; }
public string moneytotal_gross_roundoff { get; set; }
public string moneytotal_gross_all { get; set; }
public string checkouttypename { get; set; }
public string deliverytypename { get; set; }
public int orderdate { get; set; }
public int orderstateid { get; set; }
public int paymentstateid { get; set; }
public int ordertypeid { get; set; }
public string registerid { get; set; }
public int warehouseid { get; set; }
public object datereserved { get; set; }
public string currencycode { get; set; }
public Additionaldata additionaldata { get; set; }
public List<Orderitem> orderitems { get; set; }
}
public class RootObject
{
public int totalcount { get; set; }
public List<Item> items { get; set; }
}

最后反序列化它：

using System;
using Newtonsoft.Json;
using System.Collections.Generic;
public class Program
{
public static void Main()
{
string json=@"{'totalcount':103952,'items':[{'orderid':113951,'email':'','namefirst':'','namelast':'','company':'','moneyfinal_net':'95.92','moneyfinal_vat':'23.98','moneytotal_gross_roundoff':'0.00','moneytotal_gross_all':'119.90','checkouttypename':'Card','deliverytypename':'','orderdate':1554836745,'orderstateid':10,'paymentstateid':20,'ordertypeid':10,'registerid':'{AD16AEE2-235F-318A-4323-6B63EC2C40E7}','warehouseid':18,'datereserved':null,'currencycode':'NOK','additionaldata':{'pos-timezone':'Europe/Oslo','pos-staff-externalid':'4654'},'orderitems':[{'orderitemid':0,'orderitemtype':10,'productid':5486,'productname':'Test','sku':'320991800016','productattributes':'','externalinput':'','externalinputtitle':'','unitlabel':'ST','quantity':1,'decimalunitquantity':null,'moneynetpriceperunit':'63.92','moneypriceorg':'0.00','vatvalue':25,'deliveryinfo':'','moneyitemtotal_net':'63.92','moneyitemtotal_vat':'15.98','voucherid':0,'vouchercode':'','vouchername':'','moneyoriginalprice':'63.92','moneydiscountedprice':'0.00','moneydiscount':'0.00','salestaxes':[],'additionaldata':{},'decimalquantitytotal':'1.000','moneynetpriceperquantity':'63.92'}]}]}";
var  Sresponse = JsonConvert.DeserializeObject<RootObject>(json);
Console.WriteLine(Sresponse.totalcount);
foreach(var result in Sresponse.items)
{    
Console.WriteLine(result.moneyfinal_net);
Console.WriteLine(result.additionaldata.postimezone);
foreach(var result1 in result.orderitems)
{
Console.WriteLine(result1.orderitemid);
Console.WriteLine(result1.orderitemtype);
Console.WriteLine(result1.productid);
Console.WriteLine(result1.productname); 
Console.WriteLine(result1.sku);                     
}
}
}
}

输出：

103952
95.92
Europe/Oslo
0
10
5486
Test
320991800016

工作示例：https://dotnetfiddle.net/kGXBQ0