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

Method in [Library](/2.1/api/csharp/yarn/yarn.library.md)

## Summary

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

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

## Parameters

| Name                                      | Description                                           |
| ----------------------------------------- | ----------------------------------------------------- |
| `string` name                             | The name of the function.                             |
| `System.Func<T1, 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. |


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