Send & Get Data to SQL Database Using c#

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;
using System.Web.Configuration;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        DataSet objds = new DataSet();

        SqlConnection conn = new SqlConnection();
        conn.ConnectionString = WebConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

        SqlCommand cmd = new SqlCommand();
        cmd.Connection = conn;
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.CommandText = "sp_details";
        cmd.Parameters.AddWithValue("@select", "select");

        conn.Open();
        SqlDataAdapter objda = new SqlDataAdapter(cmd);
        objda.Fill(objds);
        conn.Close();
    }

    protected void btnsubmit_Click(object sender, EventArgs e)
    {
        Boolean checkresult = new Boolean();

        SqlConnection conn = new SqlConnection();
        conn.ConnectionString = WebConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

        SqlCommand cmd = new SqlCommand();
        cmd.Connection = conn;
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.CommandText = "SP_details";

        cmd.Parameters.AddWithValue("@select", "insert");
        cmd.Parameters.AddWithValue("@fname", txtfname.Text);
        cmd.Parameters.AddWithValue("@lname", txtlname.Text);

        conn.Open();
        checkresult = Convert.ToBoolean(cmd.ExecuteNonQuery());
        conn.Close();
    }
}






Connection String ----------

<connectionStrings>
    <add name="ConnectionString" connectionString="Data Source=RAJESH-PC;Persist Security Info=True;Initial Catalog=test;User ID=sa;Password=xyz" providerName="System.Data.SqlClient"/>
</connectionStrings>