Implementation of GetHashCode()

The implementation of `GetHashCode()` is different between examples. I think they should all use this:
```csharp
public override int GetHashCode() => (Name, Code).GetHashCode();
```

---
#### Document Details

⚠ *Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.*

* ID: a5fb66fb-9a33-2550-2783-7ce2a4760219
* Version Independent ID: 2e80b927-7888-1fc8-7db9-d052b33ac87a
* Content: [Enumerable.Except Method (System.Linq)](https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.except?view=netframework-4.7.2#feedback)
* Content Source: [xml/System.Linq/Enumerable.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.Linq/Enumerable.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**