Json.NET 是否缓存类型的序列化信息

Yes, it does. Json.NET在其IContractResolver个类DefaultContractResolver和CamelCasePropertyNamesContractResolver中缓存类型序列化信息.除非指定自定义合同解析程序，否则将缓存并重用此信息.

For DefaultContractResolver a global static instance is maintained internally that Json.NET uses whenever the application does not specify its own contract resolver. CamelCasePropertyNamesContractResolver, on the other hand, maintains static tables that are shared across all instances. (I believe the inconsistency arises from legacy issues; see here for details.)

Both of these types are designed to be fully thread-safe so sharing between threads should not be a problem.

如果 Select 实现和实例化您自己的协定解析器，则只有在缓存和重用协定解析器实例本身的情况下，才会缓存和重用类型信息.因此，NewtonSoft recommends:

For performance you should create a contract resolver once and reuse instances when possible. Resolving contracts is slow and implementations of IContractResolver typically cache contracts.

If memory consumption is a problem无论出于何种原因，您需要最小化缓存契约永久占用的内存，您都可以构造自己的本地实例DefaultContractResolver(或某个自定义子类)，使用该实例进行序列化，然后立即删除对它的所有引用，例如:

public class JsonExtensions
{
    public static string SerializeObjectNoCache<T>(T obj, JsonSerializerSettings settings = null)
    {
        settings = settings ?? new JsonSerializerSettings();
        bool reset = (settings.ContractResolver == null);
        if (reset)
            // To reduce memory footprint, do not cache contract information in the global contract resolver.
            settings.ContractResolver = new DefaultContractResolver();
        try
        {
            return JsonConvert.SerializeObject(obj, settings);
        }
        finally
        {
            if (reset)
                settings.ContractResolver = null;
        }
    }
}

如果您使用的是CamelCasePropertyNamesContractResolver，请使用适当的naming strategy切换到DefaultContractResolver，例如:

settings.ContractResolver = new DefaultContractResolver { NamingStrategy = new CamelCaseNamingStrategy() };

大多数高速缓存的契约存储器(100)最终将被垃圾收集.当然，通过这样做，serialization performance may suffer substantially.(包含关于例如enum种类型和数据协定属性的反映信息的一些表是全局共享的，而不是回收的.)

For further information看牛顿软件公司的Performance Tips: Reuse Contract Resolver.