The example code I’m going to include below, I’ve used before. I really like it and so I’m going to give it place here on my website, in case it may ever be helpful for you, and maybe even me again.

The first time I used something like this code example was for a function that created random passwords. By default, that function’s CharacterType parameter would include the four values Lowercase, Number, Symbol, and Uppercase. By using the parameter, you can specify which of the values you actually use, if you didn’t want to use all four. By default, the parameter included them all.

We are defining an advanced function called Test-Function with a single parameter called Type. This parameter uses ValidateSet in order that it’ll only ever accept four different parameter values, for the Type parameter. Additionally, the Type parameter actually includes a default value that includes all four of the values: FullAccess, SendAs, SendOnBehalf, and Calendar. If you ever find yourself needing an All parameter value, just use this option instead; you don’t actually need an All parameter value, you just need to include all the possible values as the default.

After the parameter inclusion, the function begins with a Foreach language construct that will evaluate each Type that been included, whether it’s all four by default, all four because someone use the parameter and entered all four possibilities (not necessary, obviously), or something less than the four options.

Inside each iteration thought the Foreach there’s a Switch statement that will be evaluated. Based on the current type value, its value will be displayed in a string that includes a hard coded value to ensure it’s correct.

Function Test-Function {
    [CmdletBinding()]
    Param (
        [Parameter()]
        [ValidateSet('FullAccess','SendAs','SendOnBehalf','Calendar')]
        [string[]]$Type = ('FullAccess','SendAs','SendOnBehalf','Calendar')
    )

    Foreach ($T in $Type) {
        Switch ($T) {
            'FullAccess' {
                "Doing $T stuff (should match FullAccess)."
            }
            'SendAs' {
                "Doing $T stuff (should match SendAs)."
            }
            'SendOnBehalf' {
                "Doing $T stuff (should match SendOnBehalf)."
            }
            'Calendar' {
                "Doing $T stuff (should match Calendar)."
            }
        } # End Switch.
    } # End Foreach.
}

PS > Test-Function
Doing FullAccess stuff (should match FullAccess).
Doing SendAs stuff (should match SendAs).
Doing SendOnBehalf stuff (should match SendOnBehalf).
Doing Calendar stuff (should match Calendar).

PS > Test-Function -Type 'FullAccess','SendAs','SendOnBehalf','Calendar' # Same as above.
Doing FullAccess stuff (should match FullAccess).
Doing SendAs stuff (should match SendAs).
Doing SendOnBehalf stuff (should match SendOnBehalf).
Doing Calendar stuff (should match Calendar).

PS > Test-Function -Type 'FullAccess','SendAs','SendOnBehalf'
Doing FullAccess stuff (should match FullAccess).
Doing SendAs stuff (should match SendAs).
Doing SendOnBehalf stuff (should match SendOnBehalf).

PS > Test-Function -Type 'FullAccess','SendAs'
Doing FullAccess stuff (should match FullAccess).
Doing SendAs stuff (should match SendAs).

PS > Test-Function -Type 'Calendar','FullAccess','SendAs'
Doing Calendar stuff (should match Calendar).
Doing FullAccess stuff (should match FullAccess).
Doing SendAs stuff (should match SendAs).

PS > Test-Function -Type 'SendOnBehalf','FullAccess','Calendar'
Doing SendOnBehalf stuff (should match SendOnBehalf).
Doing FullAccess stuff (should match FullAccess).
Doing Calendar stuff (should match Calendar).

Nothing down here, but thanks for reading all the way! Actually, here’s a bonus if you didn’t already know it. Those hard coded statements inside the Switch statement, could’ve been written a little differently.

This:

...
            'FullAccess' {
                "Doing $T stuff (should match FullAccess)."
            }
            'SendAs' {
                "Doing $T stuff (should match SendAs)."
            }
            'SendOnBehalf' {
                "Doing $T stuff (should match SendOnBehalf)."
            }
            'Calendar' {
                "Doing $T stuff (should match Calendar)."
            }
...

could’ve actually been this:

...
            'FullAccess' {
                "Doing $T stuff (should match $_)."
            }
            'SendAs' {
                "Doing $T stuff (should match $_)."
            }
            'SendOnBehalf' {
                "Doing $T stuff (should match $_)."
            }
            'Calendar' {
                "Doing $T stuff (should match $_)."
            }
...