ProcessStartInfo p = new ProcessStartInfo();

p.WorkingDirectory = @"C:WindowsSystem32";
p.FileName = @"C:WindowsSystem32cmd.exe";

p.UserName = "myUser";
p.Domain = "myDomain";

char[] password = { 'm', 'y', 'p', 'a', 's', 's'};

SecureString adminpassword = new SecureString();
foreach (char c in password)
  {
      adminpassword.AppendChar(c);
  }

p.Password = adminpassword;
p.UseShellExecute = false;
p.Verb = "runas";
Process.Start(p);