# ObserverManager<TIdentity, TObserver>.Subscribe(TIdentity, TObserver)

[Type overview](/orleans/docs/api/csharp/microsoft.orleans.core/orleans.utilities.observermanager-2/) | [Methods](/orleans/docs/api/csharp/microsoft.orleans.core/orleans.utilities.observermanager-2/methods/)

[Source](https://github.com/dotnet/orleans/blob/e4e752cedecc2976811db49802c7a999b1f1c704/src/Orleans.Core/Utils/ObserverManager.cs#L116-L131)

```csharp
public void ObserverManager<TIdentity, Subscribe(TIdentity id, TObserver observer)
```

Ensures that the provided `observer` is subscribed, renewing its subscription.

### Parameters

- `id` (`TIdentity`): The observer's identity.
- `observer` (`TObserver`): The observer.

### Exceptions

- `System.Exception`: A delegate callback throws an exception.