通过反射动态 json 序列化过滤

Question

我想为 json.net 创建一个动态合同解析器，它将在运行时间内排除字段。这个想法是传递给构造函数 something 这将排除 CreateProperties 覆盖中的某些字段。

到目前为止，我想出了传递 PropertyInfo[] 依赖于 Json / Class 属性名称相等性，这在 long 运行中不好（即我想要将 json 属性名称覆盖为更短的名称）。解决方案的另一个问题是我需要通过 PropertyInfo[]，这在我看来并不直观。

也许有一种方法可以使用 LINQ 表达式以更好的方式重写此 class。例如传递 List<Func<T,TOut>> 然后通过反射编译和提取参数。它将更加动态，但不会解决 Json / Class 属性名称相等的问题。

任何建议，我卡住了....

public class DynamicContractResolver : DefaultContractResolver
{
    private readonly PropertyInfo[] m_propertiesExclusion;
    public DynamicContractResolver(PropertyInfo[] propertiesExclusion)
    {
        m_propertiesExclusion = propertiesExclusion;
    }

    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        IList<JsonProperty> jsonProperties = base.CreateProperties(type, memberSerialization);

        IEnumerable<string> filteredOutProperties = m_propertiesExclusion.Select(i => i.Name);
        jsonProperties = jsonProperties
            .Where(i => !filteredOutProperties.Contains(i.PropertyName))
            .ToList();

        return jsonProperties;
    }
}

Answer 1

这是一个采用任意数量 Expression<Func<T, object>> 并排除它们引用的属性的实现。从表达式中提取属性名称的代码取自 this answer.

public class DynamicContractResolver<T> : DefaultContractResolver
{
    private readonly HashSet<string> propertiesToExclude;

    public DynamicContractResolver(
        params Expression<Func<T, object>>[] propertyExpressions)
    {
        this.propertiesToExclude = new HashSet<string>();

        foreach (Expression<Func<T, object>> expression in propertyExpressions)
        {
            string propertyName = GetPropertyNameFromExpression(expression);

            this.propertiesToExclude.Add(propertyName);
        }
    }

    protected override IList<JsonProperty> CreateProperties(
        Type type, MemberSerialization memberSerialization)
    {
        IList<JsonProperty> jsonProperties =
            base.CreateProperties(type, memberSerialization);

        if (typeof(T).IsAssignableFrom(type))
        {
            jsonProperties = jsonProperties
                .Where(pr => !this.propertiesToExclude.Contains(pr.PropertyName))
                .ToList();
        }

        return jsonProperties;
    }

    // 
    private string GetPropertyNameFromExpression(
        Expression<Func<T, object>> expression)
    {
        MemberExpression body = expression.Body as MemberExpression;

        if (body == null)
        {
            UnaryExpression ubody = (UnaryExpression)expression.Body;
            body = ubody.Operand as MemberExpression;
        }

        return body.Member.Name;
    }
}

这是一个使用它的例子：

var resolver = new DynamicContractResolver<MyClass>(
    mc => mc.MyIntegerProperty,
    mc => mc.MyBoolProperty);

var myClass = new MyClass
{
    MyIntegerProperty = 4,
    MyStringProperty = "HELLO",
    MyBoolProperty = true
};

var settings = new JsonSerializerSettings
{
    ContractResolver = resolver,
    Formatting = Newtonsoft.Json.Formatting.Indented
};

string serialized = JsonConvert.SerializeObject(
    myClass, settings);

Console.WriteLine(serialized);

通过反射动态 json 序列化过滤

Dynamic json serialization filtering via reflection

.net

c#

serialization

json.net