如何在 C# 中使用反射获取 Json 属性名称

Question

我有一个 class 如下所述：

public class Employee {

    [JsonProperty("emp_id")]
    public int Id {get; set;}

    [JsonProperty("emp_fname")]
    public string Name {get;set;}

    [JsonProperty("emp_lname")]
    public string LastName {get;set;} 
}

在上面的class中，我为序列化分配了Newtonsoft属性。

我有一个 class Employee 的对象，现在我想通过 JsonProperty 找到属性并获取属性的值。

例如，我想获取 JsonProprty 属性名称设置为 emp_lname

的属性的值

有没有办法使用反射找到这样的值？

Answer 1

可以使用Json.NET自己的contract resolver for this purpose. Doing so will correctly handle properties with, and without, [JsonProperty(string name)] attributes added, as well as objects with naming strategies or data contract attributes直接应用

首先添加如下方法：

public static partial class JsonExtensions
{
    static readonly IContractResolver defaultResolver = JsonSerializer.CreateDefault().ContractResolver;

    public static object GetJsonProperty<T>(T obj, string jsonName, bool exact = false, IContractResolver resolver = null)
    {
        if (obj == null)
            throw new ArgumentNullException(nameof(obj));
        resolver = resolver ?? defaultResolver;
        var contract = resolver.ResolveContract(obj.GetType()) as JsonObjectContract;
        if (contract == null)
            throw new ArgumentException(string.Format("{0} is not serialized as a JSON object", obj));
        var property = contract.Properties.GetProperty(jsonName, exact ? StringComparison.Ordinal : StringComparison.OrdinalIgnoreCase);
        if (property == null)
            throw new ArgumentException(string.Format("Property {0} was not found.", jsonName));
        return property.ValueProvider.GetValue(obj); // Maybe check JsonProperty.Readable first, and throw an exception if not?
    }
}

现在您可以：

var employee = new Employee
{
    LastName = "last name",
};

Console.WriteLine("Value of {0} is {1}.", "emp_lname", 
                  JsonExtensions.GetJsonProperty(employee, "emp_lname")); // Prints Value of emp_lname is last name.

如果您的应用默认使用驼峰式大小写 JSON 序列化，您可以像这样为 resolver 传递一个 CamelCasePropertyNamesContractResolver ：

Console.WriteLine("Value of {0} is {1}.", "emp_lname", 
                  JsonExtensions.GetJsonProperty(employee, "emp_lname", resolver : new CamelCasePropertyNamesContractResolver()));

如果您需要获取给定类型的所有 JSON 属性名称的列表，请参阅 :

public static partial class JsonExtensions
{
    public static string [] PropertyNames(Type type)
    {
        return PropertyNames(defaultResolver, type);
    }

    //Taken from this answer 
    //To 
    public static string [] PropertyNames(this IContractResolver resolver, Type type)
    {
        if (resolver == null || type == null)
            throw new ArgumentNullException();
        var contract = resolver.ResolveContract(type) as JsonObjectContract;
        if (contract == null)
            return new string[0];
        return contract.Properties.Where(p => !p.Ignored).Select(p => p.PropertyName).ToArray();
    }
}

演示 fiddle here.

如何在 C# 中使用反射获取 Json 属性名称

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如何在 C# 中使用反射获取 Json 属性 名称

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如何在 C# 中使用反射获取 Json 属性名称