# Dependency

> The ECS-related data dependencies of the system.

## Definition

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

```csharp
public JobHandle Dependency { get; set; }
```

### Remarks

Before [SystemBase.OnUpdate](/engine/7000.0/script-reference/unity/entities/systembase/onupdate.md) or [ISystem.OnUpdate](/engine/7000.0/script-reference/unity/entities/isystem/onupdate.md), the Dependency property represents the combined job handles of any job that writes to the same components that the current system reads -- or reads the same components that the current system writes to.

The [JobHandle] objects of any jobs scheduled with explicit dependencies are not combined with the system’s Dependency property. You must set the Dependency property manually to make sure that later systems receive the correct job dependencies.

[JobHandle]: https://docs.unity3d.com/ScriptReference/Unity.Jobs.JobHandle.html

Additional Resources: [SystemBase.Dependency](/engine/7000.0/script-reference/unity/entities/systembase/dependency.md)