من کد رو این طوری نوشتم

    string s = textBox1.Text;
Class1.con.Open();
Class1.com.Connection = Class1.con;
Class1.com.CommandText = "SELECT codeposti FROM [mobile_list] WHERE (city = '"+ s +"') GROUP BY codeposti ORDER BY codeposti";
OleDbDataAdapter da = new OleDbDataAdapter(Class1.com.ToString(), Class1.con);
System.Data.DataTable dt = new System.Data.DataTable();
da.Fill(dt);
Class1.con.Close();
dataGridView1.DataSource = dt;


این خطا رو میده Invalid SQL statement; expected 'DELETE', 'INSERT', 'PROCEDURE', 'SELECT', or 'UPDATE'.