> 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/3.1/api/csharp/yarn.unity/yarn.unity.dialoguerunner/yarn.unity.dialoguerunner.addfunction.md).

# AddFunction(string,Delegate)

Method in [DialogueRunner](/3.1/api/csharp/yarn.unity/yarn.unity.dialoguerunner.md)

## Summary

Add a new function that returns a value, so that it can be called from Yarn scripts.

```csharp
public void AddFunction(string name, Delegate implementation);
```

## Remarks

When this function has been registered, it can be called from your Yarn scripts like so:

```
<<if myFunction(1, 2) == true>>
myFunction returned true!
<<endif>>
```

The `call` command can also be used to invoke the function:

```
<<call myFunction(1, 2)>>
```

## Parameters

| Name                      | Description                                                                |
| ------------------------- | -------------------------------------------------------------------------- |
| `string` name             | The name of the function to add.                                           |
| `Delegate` implementation | The `System.Delegate` that should be invoked when this function is called. |

## See Also

* [Library](/3.1/api/csharp/yarn/yarn.library.md): A collection of functions that can be called from Yarn programs.