> For the complete documentation index, see [llms.txt](https://docs.yarnspinner.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.yarnspinner.dev/2.1/api/csharp/yarn.compiler.upgrader/yarn.compiler.upgrader.orderedset/yarn.compiler.upgrader.orderedset.add-1.md).

# Add(IEnumerable\<T>)

Method in [OrderedSet](/2.1/api/csharp/yarn.compiler.upgrader/yarn.compiler.upgrader.orderedset.md)

## Summary

```csharp
public void Add(IEnumerable<T> items)
```

## Parameters

| Name                                              | Description |
| ------------------------------------------------- | ----------- |
| `System.Collections.Generic.IEnumerable<T>` items |             |