Paging control for Gridview Display

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.Sql;
using System.Data.SqlClient;


/***************************
COPYRIGHT   :Ram Krishna Wagle
TITLE       :Paging in a Grid View
AUTHOR      :Ram Krishna Wagle
DESCRIPTION :To show how a simple paging could be implemented in a grid view
DATE        :March 20, 2007
***************************/
namespace PagingGrid
{
    public partial class Form1 : Form
    {
        public int currentIndex = 1; ///Variable to track the paging the gridview
        public DataTable mainDTable; 
        public DataTable tempDTable;
        public int numDocs; //no. of documents to be displayed at one screen shot
        public int totPages = 1;

        public Form1()
        {
            InitializeComponent();
            //LoadGridView();
            ColumnForPagingGrid();
            LoadGridView();
        }
        /// <summary>
        /// This functions does all the trick of paging.
        /// </summary>
        public void LoadGridView()
        { 
           
            if (currentIndex == 1)
            {
                ColumnForPagingGrid(); //loads the grid structure 
                //make the connection to the server
                
                string cStr= "Network Library=dbmssocn;Data Source=100.100.100.8,1433;Initial Catalog=dev_main_ors;User ID=sa;Password=sandman";
                SqlConnection sConn = new SqlConnection(cStr);
                SqlCommand cmdSql = new SqlCommand();

                try { sConn.Open(); }
                catch (Exception exp) {
                    MessageBox.Show(exp.ToString());// throw exp;
                }
                ///This is the query that returns the result in bulk to populate the datatable
                ///Here fire your own query that returns the results that are to be displayed in the grid

                string query = 
                " select fulltext_ref_key as [Doc Key],page_key as [Key]," +
                " fulltext_location as [Text Location], [indexed], row_number() over(order by page_key) as [RowNum]" +
                " from fulltext_info where db_id=152";
                cmdSql = sConn.CreateCommand();
                cmdSql.CommandText = query;
                SqlDataAdapter sAdp = new SqlDataAdapter(cmdSql);
                mainDTable = new DataTable();
                sAdp.Fill(mainDTable);
                btnL.Enabled = false;
                btnR.Enabled = true;
            }
            
            int totValues = mainDTable.Rows.Count; //total no. of values that are to be displyed in the paged grid.

            //To adjust the no. of entry to be shown in the grid in each view
            if (totValues <= 100)
                numDocs = 50;
            else if (totValues <= 1000 && totValues > 100)
                numDocs = 100;
            else if (totValues <= 25000 && totValues > 1000)
                numDocs = 500;
            else
                numDocs = 1000;

            //this calculation detemines the range of display in one page
            int fromValue = numDocs * (currentIndex - 1) + 1;
            int toValue = currentIndex * numDocs;

            if (toValue > totValues)
                toValue = totValues;
            if (totValues == 0)
                fromValue = 0;
            //total no. of pages
            totPages = totValues / numDocs;
            double exactPages = (double)totValues / numDocs;
            if (exactPages > totPages)
                totPages += 1;
            
            string dText = "Displaying " + fromValue + " to " + toValue + " Records of " + totValues + " Records";
            if (totValues > 0)
            {
                dispText.Text = dText;
            }

            //enables or disables the left and right button according to the current state of current index
            if (totValues < numDocs)
            {
                btnL.Enabled = false;
                btnR.Enabled = false;
            }
            else if (currentIndex * numDocs > totValues)
            {
                btnR.Enabled = false;
                btnL.Enabled = true;
            }
            else if (currentIndex > 1 && currentIndex * numDocs < totValues)
            {
                btnL.Enabled = true;
                btnR.Enabled = true;
            }

            string expression = "RowNum >=" + fromValue + " and RowNum <=" + toValue;
            tempDTable = new DataTable();
            tempDTable = mainDTable.Clone();
            foreach (DataRow dr in mainDTable.Select(expression))
                tempDTable.ImportRow(dr);

            dgvPagingGrid.Rows.Clear();
            for (int i = 0; i < tempDTable.Rows.Count; i++)
            {
                DataGridViewTextBoxCell cell1 = new DataGridViewTextBoxCell();
                cell1.Value = tempDTable.Rows[i]["indexed"].ToString();
                DataGridViewTextBoxCell cell2 = new DataGridViewTextBoxCell();
                cell2.Value = tempDTable.Rows[i]["Doc Key"].ToString();
                DataGridViewTextBoxCell cell3 = new DataGridViewTextBoxCell();
                cell3.Value = tempDTable.Rows[i]["Key"].ToString();
                DataGridViewTextBoxCell cell4 = new DataGridViewTextBoxCell();
                cell4.Value = tempDTable.Rows[i]["Text Location"].ToString();

                DataGridViewRow newRow = new DataGridViewRow();

                newRow.Cells.Add(cell1);
                newRow.Cells.Add(cell2);
                newRow.Cells.Add(cell3);
                newRow.Cells.Add(cell4);
                dgvPagingGrid.Rows.Add(newRow);
            }

            dgvPagingGrid.Columns["Indexed"].Width = 60;
            dgvPagingGrid.Columns["Doc Key"].Width =
                Math.Max(100, dgvPagingGrid.Columns["Doc Key"].GetPreferredWidth(DataGridViewAutoSizeColumnMode.AllCells, true));
            dgvPagingGrid.Columns["Key"].Width =
                dgvPagingGrid.Columns["Key"].GetPreferredWidth(DataGridViewAutoSizeColumnMode.AllCells, true);
            dgvPagingGrid.Columns["Text Location"].MinimumWidth =
                dgvPagingGrid.Columns["Text Location"].GetPreferredWidth(DataGridViewAutoSizeColumnMode.AllCells, true);
            dgvPagingGrid.Columns["Text Location"].AutoSizeMode =
                DataGridViewAutoSizeColumnMode.Fill;
            
        }

        /// <summary>
        /// Displays the format for the grid view with empty rows for the required columns
        /// </summary>
        private void ColumnForPagingGrid()
        {
            dgvPagingGrid.Columns.Clear();
            DataGridViewImageColumn iconView = new DataGridViewImageColumn();
            iconView.DefaultCellStyle.NullValue = null;
            iconView.Name = "Indexed";
            iconView.HeaderText = "Indexed";

            dgvPagingGrid.Columns.Clear();

            dgvPagingGrid.Columns.Add(iconView);
            dgvPagingGrid.Columns.Add("Doc Key", "Doc Key");
            dgvPagingGrid.Columns.Add("Key", "Key");
            dgvPagingGrid.Columns.Add("Text Location", "Text Location");

            dgvPagingGrid.Columns["Indexed"].Width = 60;
            dgvPagingGrid.Columns["Doc Key"].Width =
                Math.Max(100, dgvPagingGrid.Columns["Doc Key"].GetPreferredWidth(DataGridViewAutoSizeColumnMode.AllCells, true));
            dgvPagingGrid.Columns["Key"].Width =
                dgvPagingGrid.Columns["Key"].GetPreferredWidth(DataGridViewAutoSizeColumnMode.AllCells, true);
            dgvPagingGrid.Columns["Text Location"].MinimumWidth =
                dgvPagingGrid.Columns["Text Location"].GetPreferredWidth(DataGridViewAutoSizeColumnMode.AllCells, true);
            dgvPagingGrid.Columns["Text Location"].AutoSizeMode =
                DataGridViewAutoSizeColumnMode.Fill;
        }

        private void btnR_Click(object sender, EventArgs e)
        {
            currentIndex += 1;
            LoadGridView();
        }

        private void btnL_Click(object sender, EventArgs e)
        {
            currentIndex -= 1;
            LoadGridView();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

    }
}