this is the error "Incorrect syntax near the keyword 'Add" please help me to solve it

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;

namespace ASSIGNMENT_WORK.Forms
{
    public partial class addnumber : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btnResult_Click(object sender, EventArgs e)
        {
            int firstNumber, secondNumber, result;
            firstNumber = Convert.ToInt32(txtFirstno.Text.Trim());
            secondNumber = Convert.ToInt32(txtSecondno.Text.Trim());
            result = firstNumber + secondNumber;
            txtresult.Text = Convert.ToString(result);
            SqlConnection cnn=new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["myConnectionString"].ConnectionString);
        cnn.Open();
        SqlCommand cmd = new SqlCommand();
        cmd.CommandText = "select * from  Add";
        cmd.Connection = cnn;
        SqlDataAdapter da = new SqlDataAdapter();
        da.SelectCommand = cmd;
        DataSet ds = new DataSet();
        da.Fill(ds, " Add ");
        SqlCommandBuilder cb = new SqlCommandBuilder(da);
        DataRow drow = ds.Tables["Add"].NewRow();
        drow["result"] = txtresult.Text;
        ds.Tables["Add "].Rows.Add(drow);
        da.Update(ds, " Add ");
        string script = @"<script language=""javascript"">
        alert('Information have been Saved Successfully.......!!!!!.');
       </script>;";
        Page.ClientScript.RegisterStartupScript(this.GetType(), "myJScript1", script);

        }
    }
}