Deserializing public property with non-public setter in json.net

问题

Suppose I have the following class -

public class A 
{        
   public int P1 { get; internal set; }
}

Using json.net, I am able to serialize the type with P1 property. However, during deserialization, P1 is not set. Without modifying class A, is there an in build way to handle this? In my case, I am using a class from a different assembly and cannot modify it.

回答1:

Yes, you can use a custom ContractResolver to make the internal property writable to Json.Net. Here is the code you would need:

class CustomResolver : DefaultContractResolver
{
    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        JsonProperty prop = base.CreateProperty(member, memberSerialization);

        if (member.DeclaringType == typeof(A) && prop.PropertyName == "P1")
        {
            prop.Writable = true;
        }

        return prop;
    }
}

To use the resolver, create an instance of JsonSerializerSettings and set its ContractResolver property to a new instance of the custom resolver. Then, pass the settings to JsonConvert.DeserializeObject<T>().

Demo:

class Program
{
    static void Main(string[] args)
    {
        string json = @"{ ""P1"" : ""42"" }";

        JsonSerializerSettings settings = new JsonSerializerSettings();
        settings.ContractResolver = new CustomResolver();

        A a = JsonConvert.DeserializeObject<A>(json, settings);

        Console.WriteLine(a.P1);
    }
}

Output:

Fiddle: https://dotnetfiddle.net/1fw2lC

回答2:

After some experimenting, I've found that a property is deserialised correctly if you decorate your property with:

[JsonProperty(DefaultValueHandling = DefaultValueHandling.Include)]

Applying to the class in the original question:

public class A 
{
   [JsonProperty(DefaultValueHandling = DefaultValueHandling.Include)]        
   public int P1 { get; internal set; }
}

回答3:

This is my solution to handle in more general case:

class CustomResolver : DefaultContractResolver
{
    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        JsonProperty result = base.CreateProperty(member, memberSerialization);

        var propInfo = member as PropertyInfo;
        result.Writable |= propInfo != null 
             && propInfo.CanWrite
             && !propInfo.IsPrivate;

        return result;
    }
}

With class CInternalSetter:

class CInternalSetter
{
    public CInternalSetter()
    {
        LoggedEmployeeId3 = 10;
    }
    public int LoggedEmployeeId { get; set; }
    public int LoggedEmployeeId2 { get; internal set; }
    public int LoggedEmployeeId3 { get; }
    public override string ToString()
    {
        return JsonConvert.SerializeObject(this, Formatting.Indented);
    }
}

Then test it with against this class:

JsonSerializerSettings settings = new JsonSerializerSettings();
settings.ContractResolver = new CustomResolver();

var c = new CInternalSetter()
{
    LoggedEmployeeId = 1,
    LoggedEmployeeId2 = 2
};

var cString = JsonConvert.SerializeObject(c);

Console.WriteLine(cString);
Console.WriteLine(JsonConvert.DeserializeObject<CInternalSetter>(cString).ToString());
Console.WriteLine("-------------------------------------------");
Console.WriteLine(JsonConvert.DeserializeObject<CInternalSetter>(cString, settings).ToString());

来源：https://stackoverflow.com/questions/28802288/deserializing-public-property-with-non-public-setter-in-json-net

标签

json.net

deserialization