DirectoryInfo.GetFiles() throws an undocumented UnauthorizedAccessException

```csharp
var dir = new DirectoryInfo(@"C:\Documents and Settings");
dir.GetFiles();
```
yields:
```
System.UnauthorizedAccessException: 'Access to the path 'C:\Documents and Settings' is denied.'
```
, which is [not documented](https://docs.microsoft.com/en-us/dotnet/api/system.io.directoryinfo.getfiles?view=netframework-4.0#System_IO_DirectoryInfo_GetFiles) for the empty method signature.