我只是尝试使用 C# 中的 Newtonsoft JSON 库将文件中的一些 JSON 反序列化为对象列表。以下是 MeetingFile.txt 文件的内容:
[
{
"People": [
{
"FirstName": "Malcolm",
"LastName": "Reynolds"
},
{
"FirstName": "Hoban",
"LastName": "Washburne"
}
],
"PairDate": "1/14/2016"
}
]
下面是反序列化对象图的代码:
using (var streamReader = new StreamReader(@"C:\Temp\MeetingFile.txt"))
{
var fileContents = streamReader.ReadToEnd();
var meetingHistory = JsonConvert.DeserializeObject<List<PairHistoryItem>>(fileContents);
var serialized = JsonConvert.SerializeObject(meetingHistory);
return meetingHistory;
}
和类:
public class Person
{
public readonly string FirstName;
public readonly string LastName;
public string FullName => $"{FirstName} {LastName}";
public List<IPairHistoryItem> PairHistory;
public Person(string firstName, string lastName)
{
FirstName = firstName;
LastName = lastName;
}
}
public class PairHistoryItem
{
public List<Person> People { get; }
public DateTime PairDate { get; }
public PairHistoryItem(Person person1, Person person2, DateTime pairDate)
{
People = new List<Person> {person1, person2};
PairDate = pairDate;
}
}
但无论出于何种原因,这就是我的反序列化代码中的序列化 变量中包含的内容:
[
{
"People": [
null,
null,
{
"FirstName": "Malcolm",
"LastName": "Reynolds",
"PairHistory": null,
"FullName": "Malcolm Reynolds"
},
{
"FirstName": "Hoban",
"LastName": "Washburne",
"PairHistory": null,
"FullName": "Hoban Washburne"
}
],
"PairDate": "2016-01-14T00:00:00"
}
]
列表开头的null是从哪里来的?据我所知,我文件中的 JSON 格式正确。我是否缺少 JSON 转换器的某些设置?
最佳答案
@Nikolai Samteladze 完美地总结了问题的原因。除了更改构造函数之外,另一种可能的解决方案是将 Json.Net 配置为在反序列化期间替换现有列表,而不是重新使用它。为此,您可以设置 ObjectCreationHandling
设置为 Replace
(默认为 Auto
):
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.ObjectCreationHandling = ObjectCreationHandling.Replace;
var meetingHistory = JsonConvert.DeserializeObject<List<PairHistoryItem>>(fileContents, settings);
但是,为了使其正常工作,您还需要为 PairHistoryItem
类中的 People
属性添加一个私有(private) setter ,并用 标记它>[JsonProperty]
属性,以便 Json.Net 可以“看到”它:
public class PairHistoryItem
{
[JsonProperty]
public List<Person> People { get; private set; }
public DateTime PairDate { get; }
public PairHistoryItem(Person person1, Person person2, DateTime pairDate)
{
People = new List<Person> {person1, person2};
PairDate = pairDate;
}
}
fiddle :https://dotnetfiddle.net/Zs5GI1
关于c# - Newtonsoft 反序列化向列表添加空值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34803128/