Test-IsAdministrator

Test-IsAdministrator is a PowerShell function to determine if the current user is an administrator.

function Test-IsAdministrator {
    $Administrator = [Security.Principal.WindowsBuiltinRole]::Administrator
    $User = [Security.Principal.WindowsIdentity]::GetCurrent()
    ([Security.Principal.WindowsPrincipal]($User)).IsInRole($Administrator)
}

[Security.Principal.WindowsBuiltinRole]::Administrator returns the WindowsBuiltInRole for the Administrator.

GetCurrent() returns a WindowsIdentity object that represents the current Windows user.

WindowsPrincipal.IsInRole Method determines whether the current principal belongs to the Windows user group specified.