How to exclude property from Json Serialization

Question

I have a DTO class which I Serialize

Json.Serialize(MyClass)

How can I exclude a public property of it?

(It has to

Answer 1

You can also use the [NonSerialized] attribute

[Serializable]
public struct MySerializableStruct
{
    [NonSerialized]
    public string hiddenField;
    public string normalField;
}

From the MS docs:

Indicates that a field of a serializable class should not be serialized. This class cannot be inherited.

---

If you're using Unity for example (this isn't only for Unity) then this works with UnityEngine.JsonUtility

using UnityEngine;

MySerializableStruct mss = new MySerializableStruct 
{ 
    hiddenField = "foo", 
    normalField = "bar" 
};
Debug.Log(JsonUtility.ToJson(mss)); // result: {"normalField":"bar"}

Answer 2

If you are using Json.Net attribute [JsonIgnore] will simply ignore the field/property while serializing or deserialising.

public class Car
{
  // included in JSON
  public string Model { get; set; }
  public DateTime Year { get; set; }
  public List<string> Features { get; set; }

  // ignored
  [JsonIgnore]
  public DateTime LastModified { get; set; }
}

Or you can use DataContract and DataMember attribute to selectively serialize/deserialize properties/fields.

[DataContract]
public class Computer
{
  // included in JSON
  [DataMember]
  public string Name { get; set; }
  [DataMember]
  public decimal SalePrice { get; set; }

  // ignored
  public string Manufacture { get; set; }
  public int StockCount { get; set; }
  public decimal WholeSalePrice { get; set; }
  public DateTime NextShipmentDate { get; set; }
}

Refer http://james.newtonking.com/archive/2009/10/23/efficient-json-with-json-net-reducing-serialized-json-size for more details

Answer 3

If you are using System.Text.Json then you can use [JsonIgnore].
FQ: System.Text.Json.Serialization.JsonIgnoreAttribute

Official Microsoft Docs: JsonIgnoreAttribute

As stated here:

The library is built-in as part of the .NET Core 3.0 shared framework.
For other target frameworks, install the System.Text.Json NuGet package. The package supports:

• .NET Standard 2.0 and later versions
• .NET Framework 4.6.1 and later versions
• .NET Core 2.0, 2.1, and 2.2

Answer 4

If you are using System.Web.Script.Serialization in the .NET framework you can put a ScriptIgnore attribute on the members that shouldn't be serialized. See the example taken from here:

Consider the following (simplified) case:

public class User {
    public int Id { get; set; }
    public string Name { get; set; }
    [ScriptIgnore]
    public bool IsComplete
    {
        get { return Id > 0 && !string.IsNullOrEmpty(Name); }
    } 
} 

In this case, only the Id and the Name properties will be serialized, thus the resulting JSON object would look like this:

{ Id: 3, Name: 'Test User' }

PS. Don't forget to add a reference to "System.Web.Extensions" for this to work

Answer 5

You can use [ScriptIgnore]:

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    [ScriptIgnore]
    public bool IsComplete
    {
        get { return Id > 0 && !string.IsNullOrEmpty(Name); }
    }
}

Reference here

In this case the Id and then name will only be serialized

Answer 6

If you are not so keen on having to decorate code with Attributes as I am, esp when you cant tell at compile time what will happen here is my solution.

Using the Javascript Serializer

    public static class JsonSerializerExtensions
    {
        public static string ToJsonString(this object target,bool ignoreNulls = true)
        {
            var javaScriptSerializer = new JavaScriptSerializer();
            if(ignoreNulls)
            {
                javaScriptSerializer.RegisterConverters(new[] { new PropertyExclusionConverter(target.GetType(), true) });
            }
            return javaScriptSerializer.Serialize(target);
        }

        public static string ToJsonString(this object target, Dictionary<Type, List<string>> ignore, bool ignoreNulls = true)
        {
            var javaScriptSerializer = new JavaScriptSerializer();
            foreach (var key in ignore.Keys)
            {
                javaScriptSerializer.RegisterConverters(new[] { new PropertyExclusionConverter(key, ignore[key], ignoreNulls) });
            }
            return javaScriptSerializer.Serialize(target);
        }
    }


public class PropertyExclusionConverter : JavaScriptConverter
    {
        private readonly List<string> propertiesToIgnore;
        private readonly Type type;
        private readonly bool ignoreNulls;

        public PropertyExclusionConverter(Type type, List<string> propertiesToIgnore, bool ignoreNulls)
        {
            this.ignoreNulls = ignoreNulls;
            this.type = type;
            this.propertiesToIgnore = propertiesToIgnore ?? new List<string>();
        }

        public PropertyExclusionConverter(Type type, bool ignoreNulls)
            : this(type, null, ignoreNulls){}

        public override IEnumerable<Type> SupportedTypes
        {
            get { return new ReadOnlyCollection<Type>(new List<Type>(new[] { this.type })); }
        }

        public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
        {
            var result = new Dictionary<string, object>();
            if (obj == null)
            {
                return result;
            }
            var properties = obj.GetType().GetProperties();
            foreach (var propertyInfo in properties)
            {
                if (!this.propertiesToIgnore.Contains(propertyInfo.Name))
                {
                    if(this.ignoreNulls && propertyInfo.GetValue(obj, null) == null)
                    {
                         continue;
                    }
                    result.Add(propertyInfo.Name, propertyInfo.GetValue(obj, null));
                }
            }
            return result;
        }

        public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
        {
            throw new NotImplementedException(); //Converter is currently only used for ignoring properties on serialization
        }
    }