An excerpt from Vagrant that illustrates use of C# inside PowerShell

ShuttingDown.ps1

function ShuttingDown {
    [string]$sourceCode = @"
using System;
using System.Runtime.InteropServices;

namespace Vagrant {
    public static class RemoteManager {
        private const int SM_SHUTTINGDOWN = 0x2000;

        [DllImport("User32.dll", CharSet = CharSet.Unicode)]
        private static extern int GetSystemMetrics(int Index);

        public static bool Shutdown() {
            return (0 != GetSystemMetrics(SM_SHUTTINGDOWN));
        }
    }
}
"@
    $type = Add-Type -TypeDefinition $sourceCode -PassThru
    return $type::Shutdown()
}