C# : Populate the grid by executing SQL query or reading XML file

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace Database
{
    public partial class Form1 : Form
    {
        SqlConnection conn;
        SqlDataAdapter da;
        DataSet ds;

        public Form1()
        {
            InitializeComponent();
            conn = new SqlConnection("Data Source=Server name;Initial Catalog=database name;User ID=user; Pwd=password");
            da = new SqlDataAdapter("select * from tablename", conn);
            ds = new DataSet("MyDS");

        }

         private void DisplayButton_Click(object sender, EventArgs e)
        {        
          
            conn.Open();
            da.Fill(ds);
            conn.Close();
            dataGridView1.DataSource = ds.Tables[0];
        }

        private void SortButton_Click(object sender, EventArgs e)
        {
            DataView dview = new DataView(ds.Tables[0]);
            dview.Sort = " id DESC";
            dataGridView1.DataSource = dview;

            dview.RowFilter = "id > 10";
            dataGridView1.DataSource = dview;

            dview.RowStateFilter = DataViewRowState.Deleted;
            dataGridView1.DataSource = dview;
        }

        private void WriteXMLButton_Click(object sender, EventArgs e)
        {
            ds.WriteXml("c:\\local\\Records.xml");
        }

         private void ReadXMLButton_Click(object sender, EventArgs e)
        {
            ds.ReadXml("Records.xml");
            dataGridView1.DataSource = ds;
        }

         private void RefreshButton_Click(object sender, EventArgs e)
        {
            DataSet1 ds1 = new DataSet1();
            da.Fill(ds1);
        }      
    }
}

You can also use connection string from app.config file giveb below: