基于查询参数的条件成员序列化？

Question

我想控制我的模型中的哪些属性被序列化为我的 WebAPI2 JSON 响应，基于将查询参数与属性匹配。我主要想这样做是为了减少 GET 上的带宽，而不会导致 ViewModel 类的扩散。例如：

GET /books/1?format=summary

public class Book
{
    [SerializeFormat("summary")]
    public int Id { get; set; }

    [SerializeFormat("summary")]
    public string Title { get; set; }

    public string Contents { get; set; }
}

或

[SerializeFormat("summary","Id","Title")]
public class Book
{ ... }

为此，我可以从实现ISerializable 的自定义库派生所有模型类。在ISerializable.GetObjectData() 中，遍历所有检查属性的属性。不确定这个想法的效果。

不想重新发明这个解决方案，尽管它已经作为一个包存在。

Answer 1

一种可能性是引入可应用于属性和字段的自定义attributeJsonConditionalIncludeAttribute：

[System.AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = true, Inherited = true)]
public class JsonConditionalIncludeAttribute : System.Attribute
{
    public JsonConditionalIncludeAttribute(string filterName)
    {
        this.FilterName = filterName;
    }

    public string FilterName { get; private set; }
}

接下来，子类DefaultContractResolver，覆盖CreateProperty，并为至少应用了一个[JsonConditionalInclude]的属性返回null，这些属性都不匹配提供给合约解析器的过滤器：

public class JsonConditionalIncludeContractResolver : DefaultContractResolver
{
    public JsonConditionalIncludeContractResolver(string filterName)
    {
        this.FilterName = filterName;
    }

    public string FilterName { get; set; }

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var property = base.CreateProperty(member, memberSerialization);
        // Properties without JsonConditionalIncludeAttribute applied are serialized unconditionally.
        // Properties with JsonConditionalIncludeAttribute are serialized only if one of the attributes
        // has a matching filter name.
        var attrs = property.AttributeProvider.GetAttributes(typeof(JsonConditionalIncludeAttribute), true);
        if (attrs.Count > 0 && !attrs.Cast<JsonConditionalIncludeAttribute>().Any(a => a.FilterName == FilterName))
            return null;
        return property;
    }
}

最后，在将您的类序列化为 JSON 时，将 JsonSerializerSettings.ContractResolver 设置为您的自定义合约解析器，从您的网络请求中初始化 FilterName，例如：

public class TestClass
{
    public string Property1 { get; set; }

    [JsonConditionalInclude("summary")]
    [JsonConditionalInclude("title")]
    public string Property2 { get; set; }

    [JsonConditionalInclude("summary")]
    public string Property3 { get; set; }

    [JsonConditionalInclude("title")]
    [JsonConditionalInclude("citation")]
    public string Property4 { get; set; }

    [JsonConditionalInclude("citation")]
    public string Field1;

    public static void Test()
    {
        var test = new TestClass { Property1 = "a", Property2 = "b", Property3 = "c", Property4 = "d", Field1 = "e" };
        Test(test, "summary"); // Prints "a", "b" and "c"
        Test(test, "title");   // Prints "a", "b" and "d".
        Test(test, "citation");// Prints "e", "a" and "d"
        Test(test, null);      // Prints "e", "a", "b", "c" and "d".
    }

    public static string Test(TestClass test, string webRequestFormat)
    {
        var settings = new JsonSerializerSettings { ContractResolver = new JsonConditionalIncludeContractResolver(webRequestFormat) };

        var json = JsonConvert.SerializeObject(test, Formatting.Indented, settings);

        Debug.WriteLine(json);
        return json;
    }
}

合约解析器将应用于所有被序列化的类，而不仅仅是根类，它看起来就是你想要的。