Why/How is ManagedPipelineMode a different type when Getting vs Setting?

Question

While trying to write some scripts to manage our IIS sites, I came across some strange behaviour with the ManagedPipelineMode in IIS. My code is fairly generic, and uses Get-ItemProperty to read the old value, then Set-ItemProperty to update it if it's not the value we want.

However, if I run this:

Get-ItemProperty "IIS:\AppPools\MyAppPool" "managedPipelineMode"

I get back the string Classic. However, if I run this:

Set-ItemProperty "IIS:\AppPools\MyAppPool" "managedPipelineMode" "Classic"

I get back the error Classic is not a valid value for Int32.

So, I know I can set the value using ([int][Microsoft.Web.Administration.ManagedPipelineMode]::Classic), but I don't understand why the type seems to be different when using Get-ItemProperty vs Set-ItemProperty, or how I can query this in a way that behaves consistently.

Note: I don't really want to put a special case in for ManagedPipelineMode, as every other property seems to behave as expected. So, two questions:

1. What is this strange behaviour that allows a property to be a string when read, but int when set? Is this the case for all enums?
2. Is there any way to read/write this property using the same type, so I can write code that is able to read the value, check if it's what we want, and if not, update it?

Answer 1

Use the following values: 0 = Integrated; 1 = Classic

Set-ItemProperty "IIS:\AppPools\MyAppPool" "managedPipelineMode" "1"

Answer 2

Try using

Set-ItemProperty -Path:'IIS\AppPools\MyAppPool' -Name:'managedPipelineMode' -Value:Classic

Note the lack of quotation marks on Classic

Notes: I prefer to call argument names specifically so there is no confusion later, and if they update/change the command, wierd stuff doesn't happen

I also use the colon binding operator. This makes it absolutely clear that the value belongs to an argument of that name.