# Sandbox.SandboxSystemExtensions.WithExtension

```csharp
static string WithExtension(string path, string ext)
```

Adds or replaces the extension of `path` to `ext`.

### Parameters

- `path` (`string`): A file path with or without an extension.
- `ext` (`string`): A file extension with or without a leading period.

### Returns

`string`

Declared in [Sandbox.SandboxSystemExtensions](/api/Sandbox.SandboxSystemExtensions).
Assembly: `Sandbox.System`.