SQL multiple statements, INSERT not working
protected void btnLog_Click(object sender, EventArgs e)
{
    using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["dbConn"].ToString()))
    {
        string username = null;
        string password = null;
        string ipAddress = null;

        SymCryptography cryptic = new SymCryptography();
        SqlCommand cmdSelect = new SqlCommand();
        SqlCommand cmdLog = new SqlCommand();
        SqlDataReader myReader = null;

        cmdSelect.Connection = conn;
        cmdLog.Connection = conn;

        cmdSelect.CommandText = "SELECT * FROM uporabniki WHERE up_ime=@up_ime AND geslo=@geslo";
        cmdSelect.CommandType = CommandType.Text;
        cmdLog.CommandText = "INSERT INTO log (up_ime, ip) VALUES (@up_ime, @ip)";
        cmdLog.CommandType = CommandType.Text;

        cmdSelect.Parameters.Add("@up_ime", SqlDbType.NVarChar, 20).Value = tbUsr.Text;
        cmdSelect.Parameters.Add("@geslo", SqlDbType.NVarChar, 20).Value = cryptic.Encrypt(tbPwd.Text);
        cmdLog.Parameters.Add("@up_ime", SqlDbType.NVarChar, 20).Value = tbUsr.Text;
        cmdLog.Parameters.Add("@ip", SqlDbType.NVarChar, 20).Value = ipAddress;

        conn.Open();
        try
        {
            //cmdLog.ExecuteNonQuery();  I tried it here, but it doesn't work
            myReader = cmdSelect.ExecuteReader();
            if (myReader.Read())
            {
                username = myReader["up_ime"].ToString();
                password = myReader["geslo"].ToString();
                Session["rights"] = myReader["pravice"];
                Session["login"] = "OK";
                pravice = true;
            }
            myReader.Close();
            //cmdLog.ExecuteNonQuery();  I tried it here, but it doesn't work
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
        conn.Close();
    }
    //I tried to open connection again, but stil INSERT does not work
    /* using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["dbConn"].ToString()))
    {
        string ipAddress = null;
        SqlCommand cmdLog = new SqlCommand();
        cmdLog.Connection = conn;
        cmdLog.CommandText = "INSERT INTO log (up_ime, ip) VALUES (@up_ime, @ip)";
        cmdLog.CommandType = CommandType.Text;
        cmdLog.Parameters.Add("@up_ime", SqlDbType.NVarChar, 20).Value = tbUsr.Text;
        cmdLog.Parameters.Add("@ip", SqlDbType.NVarChar, 20).Value = ipAddress;
        conn.Open();
        try
        {
            cmdLog.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
        conn.Close();
    }

    if (pravice == true)
    {
        Response.Redirect("Default.aspx");
    }
    else
    {
        Response.Redirect("Login.aspx");
    }*/
}

INSERT INTO log (up_ime, ip) VALUES (<some time>, <test ip text>)

cmdLog.Parameters.Add("@up_ime", SqlDbType.NVarChar, 20).Value = tbUsr.Text;
    cmdLog.Parameters.Add("@ip", SqlDbType.NVarChar, 20).Value = ipAddress;

cmdLog.Parameters.Add("@up_ime", tbUsr.Text);
  cmdLog.Parameters.Add("@ip",  ipAddress);

conn.Open();

//cmdLog.ExecuteNonQuery();  I tried it here, but it doesn't work