# ImplicitChannelSubscriptionAttribute.ImplicitChannelSubscriptionAttribute(string, string?)

[Type overview](/orleans/docs/api/csharp/microsoft.orleans.broadcastchannel/orleans.implicitchannelsubscriptionattribute/) | [Constructors](/orleans/docs/api/csharp/microsoft.orleans.broadcastchannel/orleans.implicitchannelsubscriptionattribute/constructors/)

[Source](https://github.com/dotnet/orleans/blob/b7a9e3e1c9c54b3cec3a467c5734bf7744541bcf/src/Orleans.BroadcastChannel/SubscriberTable/Predicates/ImplicitChannelSubscriptionAttribute.cs#L40-L44)

```csharp
public ImplicitChannelSubscriptionAttribute(string streamNamespace, string? channelIdMapper = null)
```

Used to subscribe to the specified stream namespace.

### Parameters

- `streamNamespace` (`string`): The stream namespace to subscribe.
- `channelIdMapper` (`string?`): The name of the stream identity mapper.