# DefaultStreamIdMapper Methods

[Type overview](/orleans/docs/api/csharp/microsoft.orleans.streaming/orleans.streams.defaultstreamidmapper/)

## GetGrainKeyId(GrainBindings, StreamId) {#getgrainkeyid-orleans-metadata-grainbindings-orleans-runtime-streamid-a96b82e4}

[Dedicated page](/orleans/docs/api/csharp/microsoft.orleans.streaming/orleans.streams.defaultstreamidmapper/methods/getgrainkeyid-orleans-metadata-grainbindings-orleans-runtime-streamid-a96b82e4/)

[Source](https://github.com/dotnet/orleans/blob/e4e752cedecc2976811db49802c7a999b1f1c704/src/Orleans.Streaming/Core/DefaultStreamIdMapper.cs#L21-L47)

```csharp
public IdSpan GetGrainKeyId(GrainBindings grainBindings, StreamId streamId)
```

Gets the [GrainId](/orleans/docs/api/csharp/microsoft.orleans.core.abstractions/orleans.runtime.grainid/) which maps to the provided [StreamId](/orleans/docs/api/csharp/microsoft.orleans.streaming/orleans.runtime.streamid/)

### Parameters

- `grainBindings` (`GrainBindings`): The grain bindings.
- `streamId` (`StreamId`): The stream identifier.

### Returns

The [GrainId](/orleans/docs/api/csharp/microsoft.orleans.core.abstractions/orleans.runtime.grainid/) component.