private void button1_Click(object sender, EventArgs e)
    {
        string username = "<username>";
        string password = "<password>";

        SforceService binding = new SforceService();

        binding.Timeout = 60000;

        LoginResult lr;

        lr = binding.login(username, password);

        String authEndPoint = binding.Url;

        binding.Url = lr.serverUrl;

        binding.SessionHeaderValue = new SessionHeader();
        binding.SessionHeaderValue.sessionId = lr.sessionId;
    }