# RegisterFunction(string,Func\<T1, T2, T3, T4, TResult>)

Method in [Library](https://docs.yarnspinner.dev/2.1/api/csharp/yarn/yarn.library)

## Summary

Registers a new function that returns a value, which can be called from a Yarn program.

```csharp
public void RegisterFunction<T1, T2, T3, T4, TResult>(string name, Func<T1, T2, T3, T4, TResult> implementation)
```

## Parameters

| Name                                                  | Description                                           |
| ----------------------------------------------------- | ----------------------------------------------------- |
| `string` name                                         | The name of the function.                             |
| `System.Func<T1, T2, T3, T4, TResult>` implementation | The method to be invoked when the function is called. |

## Type Parameters

| Name    | Description                                 |
| ------- | ------------------------------------------- |
| TResult | The return type of the function.            |
| TResult | The return type of the function.            |
| T1      | The type of the function's first argument.  |
| T2      | The type of the function's second argument. |
| T3      | The type of the function's third argument.  |
| T4      | The type of the function's fourth argument. |