Passing enum values to a function in PowerShell

Question

I have a function accepting an enum value as parameter. As an example, consider something like:

(PS) > function IsItFriday([System.DayOfWeek] $dayOfWeek) { 
          


        

Answer 1

Yes, that is a rather confusing error message. I think you would understand better with an example:

Get-ChildItem -Path C:\

Notice there are no quotes around C:\ because, one, it implcitly gets converted to a string, and two, it is not necessary to enclose a path which does not contain spaces when you pass the path as a parameter to some callee.

So lets go back to your function, and change it slightly:

function IsItFriday($dayOfWeek) 
{
    $dayOfWeek.GetType()

    if ($dayOfWeek -eq [System.DayOfWeek]::Friday) 
    {
        "yes"
    } 
    else 
    {
        "no"
    }
}

IsItFriday [System.DayOkWeek]::Monday

...and the output:

IsPublic IsSerial Name                                     BaseType                                                                                        
-------- -------- ----                                     --------                                                                                        
True     True     String                                   System.Object                                                                                   
no

See what happened there? PowerShell thinks you are passing in a string instead of an enumeration value, so that's why you get Cannot convert value "[System.DayOfWeek]::Monday" because that is the literal string that gets passed in.