# EntityManagerDiffer(EntityManager, AllocatorHandle, EntityQueryDesc)

> Constructs a new EntityManagerDiffer object.

## Definition

* **Type:** Constructor
* **Namespace:** [Unity.Entities](/engine/7000.0/script-reference/unity/entities.md)
* **Assembly:** UnityEngine.EntitiesModule

```csharp
public EntityManagerDiffer(EntityManager sourceEntityManager, AllocatorManager.AllocatorHandle allocator, EntityQueryDesc entityQueryDesc = null)
```

### Parameters

**** (\[EntityManager]\(/engine/7000.0/script-reference/unity/entities/entitymanager)): The EntityManager to associate with this differ.**** (\[AllocatorHandle]\(/engine/7000.0/script-reference/unity/collections/allocatormanager/allocatorhandle)): The allocator to use for any internal memory allocations for this object.**** (\[EntityQueryDesc]\(/engine/7000.0/script-reference/unity/entities/entityquerydesc)): If non-null, the differ limits its change-tracking to the entities that this query matches.