# IGH_IndexRule interface

Namespace: [Grasshopper.Kernel.Data](https://developer.rhino3d.com/api/gh1/namespace/grasshopper.kernel.data.md) · Assembly: [Grasshopper](https://developer.rhino3d.com/api/gh1/assembly/grasshopper.md)

```cs
public interface IGH_IndexRule
```

Interface for index rules. An index rule is a way to determine whether a specific integer is considered valid, invalid or neutral. Index rules are used for selecting elements in DataTrees.

## Methods

- [Evaluate](https://developer.rhino3d.com/api/gh1/type/grasshopper.kernel.data.igh-indexrule/evaluate.md)