# IActivationWorkingSetObserver.OnActive(IActivationWorkingSetMember)

[Type overview](/orleans/docs/api/csharp/microsoft.orleans.runtime/orleans.runtime.iactivationworkingsetobserver/) | [Methods](/orleans/docs/api/csharp/microsoft.orleans.runtime/orleans.runtime.iactivationworkingsetobserver/methods/)

[Source](https://github.com/dotnet/orleans/blob/e4e752cedecc2976811db49802c7a999b1f1c704/src/Orleans.Runtime/Catalog/ActivationWorkingSet.cs#L264)

```csharp
public virtual void OnActive(IActivationWorkingSetMember member)
```

Called when an activation becomes active.

### Parameters

- `member` (`IActivationWorkingSetMember`)