# WithParameter(IType)

Method in [FunctionTypeBuilder](https://docs.yarnspinner.dev/2.2/api/csharp/yarn.compiler/yarn.compiler.functiontypebuilder)

## Summary

Adds a new parameter of type `parameterType` to the [FunctionType](https://docs.yarnspinner.dev/2.2/api/csharp/yarn.compiler/yarn.compiler.functiontypebuilder/yarn.compiler.functiontypebuilder.functiontype) .

```csharp
public FunctionTypeBuilder WithParameter(IType parameterType)
```

## Parameters

| Name                                                                                    | Description                                           |
| --------------------------------------------------------------------------------------- | ----------------------------------------------------- |
| [Yarn.IType](https://docs.yarnspinner.dev/2.2/api/csharp/yarn/yarn.itype) parameterType | The type of the new parameter to add to the function. |

## Returns

The [FunctionTypeBuilder](https://docs.yarnspinner.dev/2.2/api/csharp/yarn.compiler/yarn.compiler.functiontypebuilder) instance that received this method call.