# Requirement enum

Namespace: [Grasshopper2.Parameters](https://developer.rhino3d.com/api/gh2/namespace/grasshopper2.parameters.md) · Assembly: [Grasshopper2](https://developer.rhino3d.com/api/gh2/assembly/grasshopper2.md)

```cs
public enum Requirement
```

Enumerates the kinds of requirements component input parameters have.

## Values

| Name | Value | Description |
| --- | --- | --- |
| MustExist | 0 | The Component.Process() method is only called if the input is not null. |
| MayBeNull | 1 | The Component.Process() method is called even if the input is null. |
| MayBeMissing | 2 | The Component.Process() method is called even if the input coverage doesn't intersect with the data inside the associated input parameter. |