Неправильный синтаксис

using System;
using System.Data.SqlClient;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace WindowsFormsApp10
{
    public partial class Form1 : Form
    {
        int pageSize = 5;
        int pageNumber = 0;
        string connectionString = @"Data Source=.\; Initial Catalog=slav&alex; Integrated Security=True";
        SqlDataAdapter adapter;
        DataSet ds;
        
        public Form1()
        {
            InitializeComponent();
            dataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect;
            dataGridView1.AllowUserToAddRows = false;
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                adapter = new SqlDataAdapter(GetSql(), connection);
               
                ds = new DataSet();
                adapter.Fill(ds, "people");
                dataGridView1.DataSource = ds.Tables[0];
                dataGridView1.Columns["id"].ReadOnly = true;
            }
        }
       
 
        private void Button1_Click(object sender, EventArgs e)
        {
            if (ds.Tables["people"].Rows.Count < pageSize) return;
            pageNumber++;
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                adapter = new SqlDataAdapter(GetSql(), connection);
                ds.Tables["people"].Rows.Clear();
                adapter.Fill(ds, "people");
 
            }
        }
 
        private void Button2_Click(object sender, EventArgs e)
        {
            if (pageNumber == 0) return;
            pageNumber--;
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                adapter = new SqlDataAdapter(GetSql(), connection);
                ds.Tables["ludi"].Rows.Clear();
                adapter.Fill(ds, "people");
 
            }
        }
        private string GetSql()
        {
            return "SELECT * FROM people ORDER BY  id OFFSET ((" + pageNumber + ") * " + pageSize + ") " + "ROWS FETCH NEXT" + pageSize + "ROWS ONLY";
        }
    }