＆＃x27;收集尺寸为固定。＆＃x27;例外：System.Text.json.jsonserializer中的错误还是错误？

发布于 2025-02-10 21:50:27 字数 2075 浏览 3 评论 0 原文

我已经研究了几个，所以回答了这个例外（例如这个）没有成功。另外，重现行为的示例是我看到的最小的。作为复制此问题的控制，我有一个常数的字符串：

const string json =
@"{
    ""ArrayOfString"": [""Hello World""]
  }";

和 classa ：

class ClassA
{
    public string[] ArrayOfString { get; set; }
}

没有问题 delelialization classa 是否使用<我做代码> newtonsoft.json 或 system.text.json 。

ClassA classA;
classA = Newtonsoft.Json.JsonConvert.DeserializeObject<ClassA>(json);
classA = System.Text.Json.JsonSerializer.Deserialize<ClassA>(json);

现在，考虑 classB ，其中同一属性具有 Baseclass 中的备份存储。

class ClassB : BaseClass
{
    public string[] ArrayOfString
    {
        get => new string[] { base.SingularString };
        set
        {
            if((value != null) && (value.Length == 1))
            {
                base.SingularString = value[0];
            }
        }
    }
}
class BaseClass
{
    public string SingularString { get; set; } = "Hello World";
}

从相同的 json 源中， classB clastb 似乎并不是一个大的要求。

ClassB classB;
classB = Newtonsoft.Json.JsonConvert.DeserializeObject<ClassB>(json);
classB = System.Text.Json.JsonSerializer.Deserialize<ClassB>(json);

newtonsoft 没有任何牛肉这样做：

但是， system.text.json 当要求做同样的事情时抛出：

任何人是否有第一手知识此错误 2年前？这是重新出现的吗？还是只是犯某种错误？是的，我明白了。集合是固定的尺寸，但这为什么重要？

原文

I have studied several SO answers citing this exception (like this one) without success. Also, my example to reproduce the behavior is the most minimal that I've seen. As a control for reproducing this issue, I have this constant string:

const string json =
@"{
    ""ArrayOfString"": [""Hello World""]
  }";

And ClassA:

class ClassA
{
    public string[] ArrayOfString { get; set; }
}

There are no issues deserializing ClassA whether I do it with Newtonsoft.Json or System.Text.Json.

ClassA classA;
classA = Newtonsoft.Json.JsonConvert.DeserializeObject<ClassA>(json);
classA = System.Text.Json.JsonSerializer.Deserialize<ClassA>(json);

Now consider ClassB where the same property has a backing store in BaseClass.

class ClassB : BaseClass
{
    public string[] ArrayOfString
    {
        get => new string[] { base.SingularString };
        set
        {
            if((value != null) && (value.Length == 1))
            {
                base.SingularString = value[0];
            }
        }
    }
}
class BaseClass
{
    public string SingularString { get; set; } = "Hello World";
}

It doesn't seem like a big ask to have ClassB deserialize from the same json source.

ClassB classB;
classB = Newtonsoft.Json.JsonConvert.DeserializeObject<ClassB>(json);
classB = System.Text.Json.JsonSerializer.Deserialize<ClassB>(json);

Newtonsoft doesn't have any beef doing this:

However, System.Text.Json throws when asked to do the same thing:

Does anyone have first-hand knowledge of this bug which was closed more than 2 years ago? Is this a reemergence of that? Or am simply making an error of some kind? And yeah, I get it. The collection is a fixed size but why would that matter?

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笑看君怀她人 2025-02-17 21:50:27

这是一个固定在.NET 5的错误。请参阅plup 替换收集实例＃39442 。可以在这里看到一个工作.NET 6小提琴： https://dotnetfiddle.net/uhryjp 。

如果您必须针对.NET Core 3.1开发，则您的选项似乎包括：

为 classB 。

使用 list＆lt; string＆gt; 而不是 string [] arayofstring ：

  classB：Baseclass
{
    公共列表＆lt; string＆gt; arrayofstring
    {
        get =＆gt;新列表＆lt; string＆gt;（）{base.singularString};
        放
        {
            if（（value！= null）＆amp;＆amp;（value.count == 1））
            {
                base.singularString = value [0];
            }
        }
    }
}

（请注意，如果您仍在定位System.Text.json和Newtonsoft， list＆lt; string＆gt; 将无法与后者一起使用。请参阅Eg 当我的poco中的所有收藏都无效，当时将一些有效的json与.net newtonsoft.json component.json component P>

This is a bug that was fixed in .NET 5. See pull Replace collection instances on deserialize #39442. A working .NET 6 fiddle can be seen here: https://dotnetfiddle.net/UhRYJP.

If you must develop against .NET Core 3.1, your options would appear to include:

Introduce a custom converter for ClassB.
Use a List<string> instead of a string [] for ArrayOfString:
```
class ClassB : BaseClass
{
    public List<string> ArrayOfString
    {
        get => new List<string>() { base.SingularString };
        set
        {
            if((value != null) && (value.Count == 1))
            {
                base.SingularString = value[0];
            }
        }
    }
}
```
(Note that if you are still targeting both System.Text.Json and Newtonsoft, List<string> will not work with the latter. See e.g. Why are all the collections in my POCO are null when deserializing some valid json with the .NET Newtonsoft.Json component for why.)