ServiceStack.Text StackOverflowException with Parent/Children circular references

Question

Serialization of simple (1:1) parent/child circular references works, as noted in mythz answer here. However, I am getting a StackOverflowException when trying to serialize a parent with a list of children who hold a ref back to their parent.

I have condensed this down to bare-bones tests and test classes at my commonGib repo on GitHub.

Tests:

/// <summary>
/// Trivial business classes with a simple 1:1 circular relationship, i.e. Parent.Child, Child.Parent.
/// </summary>
[TestMethod]
public void Simple_ServiceStack()
{
    var parent = new SimpleParent() { Text = "Foo" };
    var child = new SimpleChild() { Number = 2 };

    parent.Child = child;
    child.Parent = parent;

    var parentJson = JsonSerializer.SerializeToString(parent);

    var parentTest = JsonSerializer.DeserializeFromString<SimpleParent>(parentJson);

    Assert.IsTrue(parentTest.TextEqualsFoo());
    Assert.IsTrue(parentTest.Child.NumberEqualsTwo());
}

/// <summary>
/// Test business classes more complex by having a parent with a list of children, as opposed
/// to a 1:1 relationship, i.e. Parent.Children instead of Parent.Child.
/// </summary>
[TestMethod]
public void Complex_ServiceStack()
{
    var parent = new ComplexParent() { Text = "Foo" };
    var child = new ComplexChild() { Number = 2 };

    parent.Children = new List<ComplexChild>() { child };
    child.Parent = parent;

    var parentJson = JsonSerializer.SerializeToString(parent); //Throws stack overflow

    var parentTest = JsonSerializer.DeserializeFromString<ComplexParent>(parentJson);

    Assert.IsTrue(parentTest.TextEqualsFoo());
    foreach (var childTest in parentTest.Children)
    {
        Assert.IsTrue(childTest.NumberEqualsTwo());
    }
}

/// <summary>
/// Real-world business classes wrapped around a state class.
/// </summary>
[TestMethod]
public void VeryComplex_ServiceStack()
{
    var parentState = new VeryComplexParentState() { Text = "Foo" };
    var childState = new VeryComplexChildState() { Number = 2 };

    var parent = new VeryComplexParent() { State = parentState };
    var child = new VeryComplexChild() { State = childState };

    parent.Children = new List<VeryComplexChild>() { child };
    child.Parent = parent;

    var parentJson = JsonSerializer.SerializeToString(parent); //Throws stack overflow

    var parentTest = JsonSerializer.DeserializeFromString<ComplexParent>(parentJson);

    Assert.IsTrue(parentTest.TextEqualsFoo());
    foreach (var childTest in parentTest.Children)
    {
        Assert.IsTrue(childTest.NumberEqualsTwo());
    }
}

Test classes:

#region Simple Parent/Child

public class SimpleParent
{
    public string Text { get; set; }
    public SimpleChild Child { get; set; }

    /// <summary>
    /// This is like a validation rule on the state wrapper.
    /// </summary>
    public bool TextEqualsFoo()
    {
        return Text == "Foo";
    }
}

public class SimpleChild
{
    public int Number { get; set; }
    public SimpleParent Parent { get; set; }

    /// <summary>
    /// This is like a validation rule on the state wrapper.
    /// </summary>
    public bool NumberEqualsTwo()
    {
        return Number == 2;
    }
}

#endregion

#region Complex Parent/Child

public class ComplexParent
{
    public string Text { get; set; }
    public List<ComplexChild> Children { get; set; }

    /// <summary>
    /// This is like a validation rule on the state wrapper.
    /// </summary>
    public bool TextEqualsFoo()
    {
        return Text == "Foo";
    }
}

public class ComplexChild
{
    public int Number { get; set; }
    public ComplexParent Parent { get; set; }

    /// <summary>
    /// This is like a validation rule on the state wrapper.
    /// </summary>
    public bool NumberEqualsTwo()
    {
        return Number == 2;
    }
}

#endregion

#region Very Complex Parent/Child

public abstract class BaseSerializationTestClass<TState>// : BaseSerializationTestClass
{
    public TState State { get; set; }
}


public class VeryComplexParent : BaseSerializationTestClass<VeryComplexParentState>
{
    /// <summary>
    /// This is like a validation rule on the state wrapper.
    /// </summary>
    public bool TextEqualsFoo()
    {
        return State != null && State.Text == "Foo";
    }

    public List<VeryComplexChild> Children { get; set; }
}

public class VeryComplexParentState
{
    public string Text { get; set; }

    public List<VeryComplexChildState> MyChildrenState { get; set; }
}

public class VeryComplexChild : BaseSerializationTestClass<VeryComplexChildState>
{
    /// <summary>
    /// This is like a validation rule on the state wrapper.
    /// </summary>
    public bool NumberEqualsTwo()
    {
        return State != null && State.Number == 2;
    }

    public VeryComplexParent Parent { get; set; }
}

public class VeryComplexChildState
{
    public int Number { get; set; }

    public VeryComplexParentState MyAState { get; set; }
}

#endregion

Answer 1

No. Circular references don't work. Even in your first example (Simple_ServiceStack) for the serialization I get:

{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":{"Text":"Foo","Child":{"Number":2,"Parent":}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}

That is wrong and broken (see the last "Parent":}). (tested with ServiceStack.Text 4.0.38)

As written in one of the comments:

Your example dto is not using circular references - it is using different objects for each link property

As suggested by the question you linked, use Json.NET with meta ids.