Rendering a generated table with TableLayoutPanel taking too long to finish

Question

My program is pretty straight forward in concept - it allows a user to take scores during bowling tournaments, as well as showing the players the scores through a scoreboard.

Answer 1

Well, the CellPaint event was the culprit. I was able to achieve what I wanted by negating the CellPaint event, and instead manipulating the controls in the panel so as to have the right background colors as well as size so they fill the grid.

Thank you for all your comments - they were very helpful. As per HighCore's comment, I will now be looking into WPF and I might be able to get something even slicker.

Answer 2

Some people suggested you to use a "proper technology". I would rather say "use properly the technology". Even this weird (sorry) design/implementation choice can be made to work much faster, as shown in the code below, which as you may see is handling rebuilding a table containing 100 rows x 10 columns 10 times per sec - not a big deal compared to professional grids, but far from the original implementation. Key points:
1. Enclose table rebuild with Suspend/ResumeLayout to avoid intensive recalculations during the process.
2. Use custom double buffered TableLayoutPanel to avoid flickering.
3. Custom paint the data cells to avoid allocating a lot of controls.

Since essential data related parts are missing in the code you gave us, I can't provide you exactly the same working code. Hope you can recognize and map it to your stuff.

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;

namespace Tests
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new ScoreBoardForm { WindowState = FormWindowState.Maximized });
        }
    }

    class ScoreBoardForm : Form
    {
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            players = new List<Player>();
            for (int i = 0; i < 100; i++)
                players.Add(new Player { ID = i + 1, Name = "P" + (i + 1), Total = random.Next(1000) });
            games = new List<Game>();
            for (int i = 0; i < 10; i++)
                games.Add(new Game { ID = i + 1, Name = "G" + (i + 1) });

            scoreBoardTable = new ScoreBoardTable { Dock = DockStyle.Fill, Parent = this };
            scoreBoardTable.Bounds = this.DisplayRectangle;
            UpdateScoreBoard();
            scoreBoardTable.CellPaint += OnScoreBoardTableCellPaint;

            updateTimer = new Timer { Interval = 100 };
            updateTimer.Tick += (_sender, _e) => UpdateScoreBoard();
            updateTimer.Start();
        }
        private void OnScoreBoardTableCellPaint(object sender, TableLayoutCellPaintEventArgs e)
        {
            int playerIndex = e.Row - 1, gameIndex = e.Column - 2;
            if (playerIndex >= 0 && playerIndex < players.Count && gameIndex >= 0 && gameIndex < games.Count)
            {
                using (var br = new SolidBrush(GetBackColor(e.Row)))
                    e.Graphics.FillRectangle(br, e.CellBounds);
                var score = GetScore(players[playerIndex], games[gameIndex]);
                var sf = new StringFormat { Alignment = StringAlignment.Far, LineAlignment = StringAlignment.Center };
                e.Graphics.DrawString(score.ToString(), defaultCellFont, Brushes.Black, e.CellBounds, sf);
            }
        }
        private int GetScore(Player player, Game game)
        {
            return random.Next(10000);
        }
        class ScoreBoardTable : TableLayoutPanel
        {
            public ScoreBoardTable() { DoubleBuffered = AutoScroll = true; }
        }
        TableLayoutPanel scoreBoardTable;
        Timer updateTimer;
        List<Player> players;
        List<Game> games;
        Random random = new Random();
        class Player
        {
            public int ID;
            public string Name;
            public int Total;
        }
        class Game
        {
            public int ID;
            public string Name;
        }
        private void UpdateScoreBoard()
        {
            scoreBoardTable.SuspendLayout();
            GenerateTable(games.Count + 3, players.Count + 1);
            GenerateHeaderCells();
            // Custom cell paint is much faster, but requires a good data model.
            // If you uncomment the following line, make sure to get rid of CellPaint. 
            //GenerateScoreCells();
            scoreBoardTable.ResumeLayout(true);
        }
        private void GenerateTable(int columnCount, int rowCount)
        {
            scoreBoardTable.Controls.Clear();
            scoreBoardTable.ColumnStyles.Clear();
            scoreBoardTable.RowStyles.Clear();
            scoreBoardTable.ColumnCount = columnCount;
            scoreBoardTable.RowCount = rowCount;

            // Columns
            // Ranking
            scoreBoardTable.ColumnStyles.Add(new ColumnStyle(SizeType.Absolute, 30));
            // Name 
            scoreBoardTable.ColumnStyles.Add(new ColumnStyle(SizeType.AutoSize));
            // Games
            var percent = (columnCount - 3) / (float)columnCount;
            for (int col = 2; col < columnCount - 1; col++)
                scoreBoardTable.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, percent));
            // Totals
            scoreBoardTable.ColumnStyles.Add(new ColumnStyle(SizeType.AutoSize));

            // Rows
            // Header
            scoreBoardTable.RowStyles.Add(new RowStyle(SizeType.Absolute, 50));
            // Players
            for (int row = 1; row < rowCount; row++)
                scoreBoardTable.RowStyles.Add(new RowStyle(SizeType.AutoSize));
        }
        private void GenerateHeaderCells()
        {
            Color backColor = Color.DarkGray, foreColor;
            int row, col;
            // Header
            row = 0;
            foreColor = Color.White;
            col = 0;
            AddCell(row, col++, "rank", "", foreColor, backColor);
            AddCell(row, col++, "playerName", "Player", foreColor, backColor);
            foreach (var game in games)
                AddCell(row, col++, "gameName" + game.ID, game.Name, foreColor, backColor);
            AddCell(row, col, "totalColumn", "Totals", foreColor, backColor);
            // Rows
            foreColor = Color.Black;
            row++;
            foreach (var player in players)
            {
                backColor = GetBackColor(row);
                AddCell(row, 0, "playerRank_" + player.ID, "", foreColor, backColor, ContentAlignment.MiddleLeft);
                AddCell(row, 1, "playerName_" + player.ID, player.Name, foreColor, backColor, ContentAlignment.MiddleLeft);
                AddCell(row, scoreBoardTable.ColumnCount, "playerTotal_" + player.ID, player.Total.ToString(), foreColor, backColor, ContentAlignment.MiddleRight);
                row++;
            }
        }
        private void GenerateScoreCells()
        {
            var foreColor = Color.Black;
            int row = 1;
            foreach (var player in players)
            {
                var backColor = GetBackColor(row);
                int col = 2;
                foreach (var game in games)
                {
                    var score = GetScore(player, game);
                    AddCell(row, col, "score_" + player.ID + "_" + game.ID, score.ToString(), foreColor, backColor, ContentAlignment.MiddleRight, false);
                    col++;
                }
                row++;
            }
        }
        static readonly Font defaultCellFont = new Font("Microsoft Sans Serif", 25, FontStyle.Bold);
        private Label AddCell(int row, int col, string name, string text, Color foreColor, Color backColor, ContentAlignment textAlign = ContentAlignment.MiddleCenter, bool autoSize = true)
        {
            var label = new Label();
            label.Name = name;
            label.Text = text;
            label.BackColor = backColor;
            label.ForeColor = foreColor;
            label.Font = defaultCellFont;
            label.TextAlign = textAlign;
            label.AutoSize = autoSize;
            label.Margin = new Padding(0);
            label.Dock = DockStyle.Fill;
            scoreBoardTable.Controls.Add(label, col, row);
            return label;
        }
        static Color GetBackColor(int row)
        {
            if (row % 2 == 0) //even row
                return Color.Yellow;
            else //odd row
                return Color.LightGreen;
        }
    }
}

EDIT And here is equivalent implementation using DataGridView (note that now the number of rows (players) are ten times more at the same refresh rate):

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;

namespace Tests
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new ScoreBoardForm { WindowState = FormWindowState.Maximized });
        }
    }

    class ScoreBoardForm : Form
    {
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            players = new List<Player>();
            for (int i = 0; i < 1000; i++)
                players.Add(new Player { ID = i + 1, Name = "P" + (i + 1), Total = random.Next(1000) });
            games = new List<Game>();
            for (int i = 0; i < 10; i++)
                games.Add(new Game { ID = i + 1, Name = "G" + (i + 1) });

            InitScoreBoard();
            UpdateScoreBoard();

            updateTimer = new Timer { Interval = 100 };
            updateTimer.Tick += (_sender, _e) => UpdateScoreBoard();
            updateTimer.Start();
        }

        DataGridView scoreBoardTable;
        Timer updateTimer;
        List<Player> players;
        List<Game> games;
        Random random = new Random();
        class Player
        {
            public int ID;
            public string Name;
            public int Total;
        }
        class Game
        {
            public int ID;
            public string Name;
        }
        private int GetScore(Player player, Game game)
        {
            return random.Next(10000);
        }
        void InitScoreBoard()
        {
            scoreBoardTable = new DataGridView { Dock = DockStyle.Fill, Parent = this };
            scoreBoardTable.Font = new Font("Microsoft Sans Serif", 25, FontStyle.Bold);
            scoreBoardTable.SelectionMode = DataGridViewSelectionMode.FullRowSelect;
            scoreBoardTable.MultiSelect = false;
            scoreBoardTable.CellBorderStyle = DataGridViewCellBorderStyle.None;
            scoreBoardTable.BackgroundColor = Color.Honeydew;
            scoreBoardTable.ForeColor = Color.Black;
            scoreBoardTable.AllowUserToAddRows = scoreBoardTable.AllowUserToDeleteRows = scoreBoardTable.AllowUserToOrderColumns = scoreBoardTable.AllowUserToResizeRows = false;
            scoreBoardTable.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.AllCells;
            scoreBoardTable.AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.AllCells;
            scoreBoardTable.RowHeadersVisible = false;
            scoreBoardTable.EnableHeadersVisualStyles = false;
            var style = scoreBoardTable.DefaultCellStyle;
            style.SelectionForeColor = style.SelectionBackColor = Color.Empty;
            style = scoreBoardTable.ColumnHeadersDefaultCellStyle;
            style.SelectionForeColor = style.SelectionBackColor = Color.Empty;
            style.BackColor = Color.Navy;
            style.ForeColor = Color.White;
            style = scoreBoardTable.RowHeadersDefaultCellStyle;
            style.SelectionForeColor = style.SelectionBackColor = Color.Empty;
            style = scoreBoardTable.RowsDefaultCellStyle;
            style.SelectionForeColor = style.ForeColor = Color.Black;
            style.SelectionBackColor = style.BackColor = Color.Yellow;
            style = scoreBoardTable.AlternatingRowsDefaultCellStyle;
            style.SelectionForeColor = style.ForeColor = Color.Black;
            style.SelectionBackColor = style.BackColor = Color.LightGreen;
            scoreBoardTable.CellFormatting += OnScoreBoardCellFormatting;
        }
        private void UpdateScoreBoard()
        {
            scoreBoardTable.ColumnCount = 3 + games.Count;
            for (int c = 0; c < scoreBoardTable.ColumnCount; c++)
            {
                var col = scoreBoardTable.Columns[c];
                if (c == 0)
                {
                    col.Name = "Rank";
                    col.HeaderText = "";
                    col.AutoSizeMode = DataGridViewAutoSizeColumnMode.None;
                    col.Width = 48;
                }
                else if (c == 1)
                {
                    col.Name = "Player";
                    col.HeaderText = "Player";
                    col.DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleLeft;
                }
                else if (c == scoreBoardTable.ColumnCount - 1)
                {
                    col.Name = "Totals";
                    col.HeaderText = "Totals";
                    col.DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleRight;
                    //col.AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;
                }
                else
                {
                    var game = games[c - 2];
                    col.Name = "Game_" + game.ID;
                    col.HeaderText = game.Name;
                    col.DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleRight;
                    //col.AutoSizeMode = DataGridViewAutoSizeColumnMode.DisplayedCells;
                }
            }
            scoreBoardTable.RowCount = players.Count;
            scoreBoardTable.AutoResizeColumnHeadersHeight();
            scoreBoardTable.Invalidate();
        }
        private void OnScoreBoardCellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
        {
            var player = players[e.RowIndex];
            int col = e.ColumnIndex;
            if (col == 0)
                e.Value = "";
            else if (col == 1)
                e.Value = player.Name;
            else if (col == scoreBoardTable.ColumnCount - 1)
                e.Value = player.Total.ToString();
            else
            {
                var game = games[col - 2];
                e.Value = GetScore(player, game).ToString();
            }
            e.FormattingApplied = true;
        }
    }
}