concept Add - Type in category powershell

This is an excerpt from Manning's book Windows PowerShell in Action, Third Edition. Login to get full access to this book.

An enum type in .NET is a way of creating a fixed set of name-value constants. The ability to define these types is missing from PowerShell prior to version 5.0 (see chapter 19), but you can work around this by using Add-Type. You’ll define an enum that can be used to specify a coffee order. You’ll constrain the types of coffee orders you’ll allow to Latte, Mocha, Americano, Cappuccino, or Espresso. First, set a variable to the list of drink types:

PS> $beverages = 'Latte, Mocha, Americano, Cappuccino, Espresso'

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Pass a string to Add-Type that contains the fragment of C# needed to define an enum type:

PS>  Add-Type "public enum BeverageType { $beverages }"
Add-Type : Cannot add type. The type name 'BeverageType' already exists.
At line:1 char:1
+ Add-Type "public enum BeverageType { $beverages }"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (BeverageType:String)
[Add-Type], Exception    + FullyQualifiedErrorId : TYPE_ALREADY_
   EXISTS,Microsoft.PowerShell.Commands.AddTypeCommand

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