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# WithVariadicParameterType(IType?)

Method in [FunctionTypeBuilder](/3.1/api/csharp/yarn.compiler/yarn.compiler.functiontypebuilder.md)

## Summary

Sets the [VariadicParameterType](/3.1/api/csharp/yarn/yarn.functiontype/yarn.functiontype.variadicparametertype.md) of the [FunctionType](/3.1/api/csharp/yarn.compiler/yarn.compiler.functiontypebuilder/yarn.compiler.functiontypebuilder.functiontype.md) .

```csharp
public FunctionTypeBuilder WithVariadicParameterType(IType? variadicParameterType)
```

## Parameters

| Name                                                                   | Description                                           |
| ---------------------------------------------------------------------- | ----------------------------------------------------- |
| [Yarn.IType](/3.1/api/csharp/yarn/yarn.itype.md) variadicParameterType | The variadic parameter type to apply to the function. |

## Returns

The [FunctionTypeBuilder](/3.1/api/csharp/yarn.compiler/yarn.compiler.functiontypebuilder.md) instance that received this method call.