问题描述

我使用 JSON.NET 作为我的主要序列化程序.

I'm using JSON.NET as my main serializer.

这是我的模型，看我设置了一些 JSONProperties 和一个 DefaultValue.

This is my model, look that I've setted some JSONProperties and a DefaultValue.

public class AssignmentContentItem
{
    [JsonProperty("Id")]
    public string Id { get; set; }
    [JsonProperty("Qty")]
    [DefaultValue(1)]
    public int Quantity { get; set; }
}

当我序列化一个 List 时，它做得很好:

When I serialize a List<AssignmentContentItem>, it doing a good work:

private static JsonSerializerSettings s = new JsonSerializerSettings
{
    DefaultValueHandling = DefaultValueHandling.Ignore,
    NullValueHandling = NullValueHandling.Ignore
};

输出:

[{"Id":"Q0"},{"Id":"Q4"},{"Id":"Q7"}]

但是当我想反序列化这个 jsonContent 时，属性 Qty 总是 0 并且没有设置为默认值.我的意思是，当我反序列化 jsonContent 时，数量的 DefaultValue 应该是 1 而不是 0.

But when I'd like to deserialize this jsonContent, the property Qty is always 0 and is not set to the default value. I mean, when I deserialize that jsonContent, as DefaultValue for Quantity should be one instead of 0.

public static List<AssignmentContentItem> DeserializeAssignmentContent(string jsonContent)
{
    return JsonConvert.DeserializeObject<List<AssignmentContentItem>>(jsonContent, s);
}

我该怎么办

推荐答案

DefaultValue 属性没有设置属性的值.看到这个问题:.NET DefaultValue 属性

The DefaultValue attribute does not set the value of the property. See this question: .NET DefaultValue attribute

最好在构造函数中设置值:

What you might be better off doing is setting the value in the constructor:

public class AssignmentContentItem
{
    [JsonProperty("Id")]
    public string Id { get; set; }
    [JsonProperty("Qty")]
    public int Quantity { get; set; }

    public AssignmentContentItem()
    {
        this.Quantity = 1;
    }
}

这一行在哪里:

AssignmentContentItem item =
    JsonConvert.DeserializeObject<AssignmentContentItem>("{"Id":"Q0"}");

导致 AssignmentContentItem 的 Quantity 设置为 1.

Results in an AssignmentContentItem with its Quantity set to 1.

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