问题描述
我正在使用 Newtonsoft.Json 从一组类中创建一个 JSON 文件.创建的文件非常大，因此我为属性创建了 JsonProperty 以减小大小，并为某些数据类型添加了 JsonIgnore 和自定义格式.
I am creating a JSON file with Newtonsoft.Json from a set of classes. The file created is very large, so I have created JsonProperty's for the properties to reduce the size and added JsonIgnore and custom formatting for some datatypes.
结果是从 24MB 减少到 1MB，这很棒；但是，我希望选择在运行时生成完整版本或缩减属性版本.
The result is a reduction from 24MB to 1MB, which is great; however, I'd like the option to produce either the full version or the reduced property version at runtime.
无论如何我可以让序列化程序选择性地使用属性吗?
Is there anyway I can get the serializer to optionally use the attributes?
推荐答案
是的，这可以使用自定义 ContractResolver 来完成.
Yes, this can be done using a custom ContractResolver.
你没有展示任何代码，所以我只是举个例子.假设我有一个类 Foo ，如下所示.我想要序列化输出中的 Id 和 Name 属性，但我绝对对 AlternateName 和 Color.我已经用 [JsonIgnore] 标记了它们.我希望出现描述，但有时这会变得很长，所以我使用了自定义 JsonConverter 来限制它的长度.我还想为描述使用较短的属性名称，所以我用 [JsonProperty("Desc")] 对其进行了标记.
You didn't show any code, so I'll just make up an example. Let's say I have a class Foo as shown below. I want the Id and Name properties in the serialization output, but I'm definitely not interested in the AlternateName and Color. I've marked those with [JsonIgnore]. I want the description to appear, but sometimes this can get really long, so I've used a custom JsonConverter to limit its length. I also want to use a shorter property name for the description, so I've marked it with [JsonProperty("Desc")].
class Foo
{
public int Id { get; set; }
public string Name { get; set; }
[JsonIgnore]
public string AlternateName { get; set; }
[JsonProperty("Desc")]
[JsonConverter(typeof(StringTruncatingConverter))]
public string Description { get; set; }
[JsonIgnore]
public string Color { get; set; }
}
当我序列化上述实例时...
When I serialize an instance of the above...
Foo foo = new Foo
{
Id = 1,
Name = "Thing 1",
AlternateName = "The First Thing",
Description = "This is some lengthy text describing Thing 1 which you'll no doubt find very interesting and useful.",
Color = "Yellow"
};
string json = JsonConvert.SerializeObject(foo, Formatting.Indented);
...我得到这个输出:
...I get this output:
{
"Id": 1,
"Name": "Thing 1",
"Desc": "This is some lengthy text describing Thing 1 "
}
现在，假设我有时想获得完整的 JSON 输出，而忽略了我的自定义.我可以使用自定义 ContractResolver 以编程方式取消应用"类中的属性.这是解析器的代码:
Now, let's say that I sometimes want to get the full JSON output, ignoring my customizations. I can use a custom ContractResolver to programmatically "unapply" the attributes from the class. Here's the code for the resolver:
class IgnoreJsonAttributesResolver : DefaultContractResolver
{
protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
{
IList<JsonProperty> props = base.CreateProperties(type, memberSerialization);
foreach (var prop in props)
{
prop.Ignored = false; // Ignore [JsonIgnore]
prop.Converter = null; // Ignore [JsonConverter]
prop.PropertyName = prop.UnderlyingName; // restore original property name
}
return props;
}
}
要使用解析器，我将其添加到 JsonSerializerSettings 并将设置传递给序列化器，如下所示:
To use the resolver, I add it to the JsonSerializerSettings and pass the settings to the serializer like this:
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.ContractResolver = new IgnoreJsonAttributesResolver();
settings.Formatting = Formatting.Indented;
string json = JsonConvert.SerializeObject(foo, settings);
输出现在包括被忽略的属性，并且描述不再被截断:
The output now includes the ignored properties, and the description is no longer truncated:
{
"Id": 1,
"Name": "Thing 1",
"AlternateName": "The First Thing",
"Description": "This is some lengthy text describing Thing 1 which you'll no doubt find very interesting and useful.",
"Color": "Yellow"
}
完整演示:https://dotnetfiddle.net/WZpeWt
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