---
title: Circular references
description: Handle parent-child graphs that reference each other using OmitOnRecursionBehavior.
---

By default AutoFixture throws when it detects a circular object graph.

## Example scenario

`TreeNode` has a `Parent` property that points back to another node. A plain `Create<TreeNode>()` triggers infinite recursion detection.

## Example

Default behavior throws:

```csharp
var fixture = new Fixture();

Assert.ThrowsAny<ObjectCreationException>(() => fixture.Create<TreeNode>());
```

Replace the default throwing behavior to omit recursive properties:

```csharp
fixture.Behaviors
    .OfType<ThrowingRecursionBehavior>()
    .ToList()
    .ForEach(b => fixture.Behaviors.Remove(b));
fixture.Behaviors.Add(new OmitOnRecursionBehavior());

var node = fixture.Create<TreeNode>();

Assert.NotNull(node);
```

## How it works

- `ThrowingRecursionBehavior` — default; fails fast on cycles
- `OmitOnRecursionBehavior` — stops recursion and leaves the recursive property unset
- Remove the throwing behavior before adding the omit behavior

See also [Behaviors](/docs/fundamentals/behaviors).

## Next steps

- [Behaviors](/docs/fundamentals/behaviors)
- [Specimen graphs](/docs/fundamentals/specimen-graphs)

## API

- [`ThrowingRecursionBehavior`](/api/autofixture/5-0-0-rc-1/autofixture.throwingrecursionbehavior)
- [`OmitOnRecursionBehavior`](/api/autofixture/5-0-0-rc-1/autofixture.omitonrecursionbehavior)