C#

System.Diagnostics.ProcessStartInfo _ps = new System.Diagnostics.ProcessStartInfo();

_ps.FileName = _command;
_ps.CreateNoWindow = false;
_ps.Arguments = _arguments;
_ps.UseShellExecute = false;

//Load the SecureString (This can be worst way)
SecureString _psw = new SecureString();

string _password = "123456";
foreach (char Character in _password.ToCharArray())
{
    _psw.AppendChar(Character);
}

_psw.MakeReadOnly();

_ps.LoadUserProfile = false;
_ps.UserName = "User";
_ps.Password = _psw;

System.Diagnostics.Process _process = new System.Diagnostics.Process();
_process.Start(_ps);
_process.WaitForExit();