This is possible in Json.NET using some coordination between the JsonWriter
and the serializer’s ContractResolver
.
A custom JsonWriter
increments a counter when an object is started and then decrements it again when it ends.
public class CustomJsonTextWriter : JsonTextWriter
{
public CustomJsonTextWriter(TextWriter textWriter) : base(textWriter) {}
public int CurrentDepth { get; private set; }
public override void WriteStartObject()
{
CurrentDepth++;
base.WriteStartObject();
}
public override void WriteEndObject()
{
CurrentDepth--;
base.WriteEndObject();
}
}
A custom ContractResolver
applies a special ShouldSerialize
predicate on all properties that will be used to verify the current depth.
public class CustomContractResolver : DefaultContractResolver
{
private readonly Func<bool> _includeProperty;
public CustomContractResolver(Func<bool> includeProperty)
{
_includeProperty = includeProperty;
}
protected override JsonProperty CreateProperty(
MemberInfo member, MemberSerialization memberSerialization)
{
var property = base.CreateProperty(member, memberSerialization);
var shouldSerialize = property.ShouldSerialize;
property.ShouldSerialize = obj => _includeProperty() &&
(shouldSerialize == null ||
shouldSerialize(obj));
return property;
}
}
The following method shows how these two custom classes work together.
public static string SerializeObject(object obj, int maxDepth)
{
using (var strWriter = new StringWriter())
{
using (var jsonWriter = new CustomJsonTextWriter(strWriter))
{
Func<bool> include = () => jsonWriter.CurrentDepth <= maxDepth;
var resolver = new CustomContractResolver(include);
var serializer = new JsonSerializer {ContractResolver = resolver};
serializer.Serialize(jsonWriter, obj);
}
return strWriter.ToString();
}
}
The following test code demonstrates limiting the maximum depth to 1 and 2 levels respectively.
var obj = new Node {
Name = "one",
Child = new Node {
Name = "two",
Child = new Node {
Name = "three"
}
}
};
var txt1 = SerializeObject(obj, 1);
var txt2 = SerializeObject(obj, 2);
public class Node
{
public string Name { get; set; }
public Node Child { get; set; }
}