[C#] Hướng dẫn tạo combobox autocomplete

// Copyright © Serge Weinstock 2014.
//
// This library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this library.  If not, see <http://www.gnu.org/licenses/>.

using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
using ComboBox = System.Windows.Forms.ComboBox;

namespace SergeUtils
{
    /// <summary>
    /// This is a combobox with a suggestion list à la "Sublime Text"
    /// 
    /// Searches are made against the pattern in the combo textbox by matching
    /// all the characters in the pattern in the right order but not consecutively
    /// </summary>
    public class EasyCompletionComboBox : ComboBox
    {
        #region fields and properties
        /// <summary>our custom drowp down control</summary>
        private readonly DropdownControl m_dropDown;
        /// <summary>the suggestion list inside the drop down control</summary>
        private readonly ListBox m_suggestionList;
        /// <summary>the bold font used for drawing strings in the listbox</summary>
        private Font m_boldFont;
        /// <summary>Allows to know if the last text change is triggered by the keyboard</summary>
        private bool m_fromKeyboard;
        /// <summary>How do we match user input to strings?</summary>
        private StringMatchingMethod m_matchingMethod;
        #endregion

        /// <summary>
        /// constructor
        /// </summary>
        public EasyCompletionComboBox()
        {
            m_matchingMethod = StringMatchingMethod.NoWildcards;
            // we're overriding these
            DropDownStyle = ComboBoxStyle.DropDown;
            AutoCompleteMode = AutoCompleteMode.None;
            // let's build our suggestion list
            m_suggestionList = new ListBox
            {
                DisplayMember = "Text",
                TabStop = false, 
                Dock = DockStyle.Fill,
                DrawMode = DrawMode.OwnerDrawFixed,
                IntegralHeight = true,
                Sorted = Sorted,
            };
            m_suggestionList.Click += onSuggestionListClick;
            m_suggestionList.DrawItem += onSuggestionListDrawItem;
            FontChanged += onFontChanged;
            m_suggestionList.MouseMove += onSuggestionListMouseMove;
            m_dropDown = new DropdownControl(m_suggestionList);
            onFontChanged(null, null);
        }

        /// <summary>
        /// <see cref="ComboBox.Dispose(bool)"/>
        /// </summary>
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (m_boldFont != null)
                {
                    m_boldFont.Dispose();
                }
                m_dropDown.Dispose();
            }
            base.Dispose(disposing);
        }

        #region size and position of suggest box
        /// <summary>
        /// <see cref="ComboBox.OnLocationChanged(EventArgs)"/>
        /// </summary>
        protected override void OnLocationChanged(EventArgs e)
        {
            base.OnLocationChanged(e);
            hideDropDown();
        }

        /// <summary>
        /// <see cref="ComboBox.OnSizeChanged(EventArgs)"/>
        /// </summary>
        protected override void OnSizeChanged(EventArgs e)
        {
            base.OnSizeChanged(e);
            m_dropDown.Width = Width;
        }
        #endregion

        #region visibility of suggest box
        /// <summary>
        /// Shows the drop down.
        /// </summary>
        public void showDropDown()
        {
            if (DesignMode)
            {
                return;
            }
            // Hide the "standard" drop down if any
            if (base.DroppedDown)
            {
                BeginUpdate();
                // setting DroppedDown to false may select an item
                // so we save the editbox state
                string oText = Text;
                int selStart = SelectionStart;
                int selLen = SelectionLength;

                // close the "standard" dropdown
                base.DroppedDown = false;
                
                // and restore the contents of the editbox
                Text = oText;
                Select(selStart, selLen);
                EndUpdate();
            }
            // pop it up and resize it
            int h = Math.Min(MaxDropDownItems, m_suggestionList.Items.Count) * m_suggestionList.ItemHeight;
            m_dropDown.Show(this, new Size(DropDownWidth, h));
        }

        /// <summary>
        /// Hides the drop down.
        /// </summary>
        public void hideDropDown()
        {
            if (m_dropDown.Visible)
            {
                m_dropDown.Close();
            }
        }

        /// <summary>
        /// <see cref="ComboBox.OnLostFocus(EventArgs)"/>
        /// </summary>
        protected override void OnLostFocus(EventArgs e)
        {
            if (!m_dropDown.Focused && !m_suggestionList.Focused)
            {
                hideDropDown();
            }
            base.OnLostFocus(e);
        }

        /// <summary>
        /// <see cref="ComboBox.OnDropDown(EventArgs)"/>
        /// </summary>
        protected override void OnDropDown(EventArgs e)
        {
            hideDropDown();
            base.OnDropDown(e);
        }
        #endregion

        #region keystroke and mouse events
        /// <summary>
        /// Called when the user clicks on an item in the list
        /// </summary>
        private void onSuggestionListClick(object sender, EventArgs e)
        {
            m_fromKeyboard = false;
            StringMatch sel = (StringMatch)m_suggestionList.SelectedItem;
            Text = sel.Text;
            Select(0, Text.Length);
            Focus();
        }

        /// <summary>
        /// Process command keys
        /// </summary>
        protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
        {
            if ((keyData == Keys.Tab) && (m_dropDown.Visible))
            {
                // we change the selection but will also allow the navigation to the next control
                if (m_suggestionList.Text.Length != 0)
                {
                    Text = m_suggestionList.Text;
                }
                Select(0, Text.Length);
                hideDropDown();
            }
            return base.ProcessCmdKey(ref msg, keyData);
        }

        /// <summary>
        /// if the dropdown is visible some keystrokes
        /// should behave in a custom way
        /// </summary>
        protected override void OnKeyDown(KeyEventArgs e)
        {
            m_fromKeyboard = true;

            if (!m_dropDown.Visible)
            {
                base.OnKeyDown(e);
                return;
            }
            switch (e.KeyCode)
            {
                case Keys.Down:
                    if (m_suggestionList.SelectedIndex < 0)
                    {
                        m_suggestionList.SelectedIndex = 0;
                    }
                    else if (m_suggestionList.SelectedIndex < m_suggestionList.Items.Count - 1)
                    {
                        m_suggestionList.SelectedIndex++;
                    }
                    break;
                case Keys.Up:
                    if (m_suggestionList.SelectedIndex > 0)
                    {
                        m_suggestionList.SelectedIndex--;
                    }
                    else if (m_suggestionList.SelectedIndex < 0)
                    {
                        m_suggestionList.SelectedIndex = m_suggestionList.Items.Count - 1;
                    }
                    break;
                case Keys.Enter:
                    if (m_suggestionList.Text.Length != 0)
                    {
                        Text = m_suggestionList.Text;
                    }
                    Select(0, Text.Length);
                    hideDropDown();
                    break;
                case Keys.Escape:
                    hideDropDown();
                    break;
                default:
                    base.OnKeyDown(e);
                    return;
            }
            e.Handled = true;
            e.SuppressKeyPress = true;
        }

        /// <summary>
        /// We need to know if the last text changed event was due to one of the dropdowns 
        /// or to the keyboard
        /// </summary>
        /// <param name="e"></param>
        protected override void OnDropDownClosed(EventArgs e)
        {
            m_fromKeyboard = false;
            base.OnDropDownClosed(e);
        }

        /// <summary>
        /// this were we can make suggestions
        /// </summary>
        /// <param name="e"></param>
        protected override void OnTextChanged(EventArgs e)
        {
            base.OnTextChanged(e);


            if (!m_fromKeyboard || !Focused)
            {
                return;
            }

            m_suggestionList.BeginUpdate();
            m_suggestionList.Items.Clear();
            StringMatcher matcher = new StringMatcher(MatchingMethod, Text);
            foreach (object item in Items)
            {
                StringMatch sm = matcher.Match(GetItemText(item));
                if (sm != null)
                {
                    m_suggestionList.Items.Add(sm);
                }
            }
            m_suggestionList.EndUpdate();

            bool visible = m_suggestionList.Items.Count != 0;

            if (m_suggestionList.Items.Count == 1 && ((StringMatch)m_suggestionList.Items[0]).Text.Length == Text.Trim().Length)
            {
                StringMatch sel = (StringMatch)m_suggestionList.Items[0];
                Text = sel.Text;
                Select(0, Text.Length);
                visible = false;
            }

            if (visible)
            {
                showDropDown();
            }
            else
            {
                hideDropDown();                
            }
            
            m_fromKeyboard = false;
        }

        /// <summary>
        /// We highlight the selection under the mouse in the suggestion listbox
        /// </summary>
        private void onSuggestionListMouseMove(object sender, MouseEventArgs e)
        {
            int idx = m_suggestionList.IndexFromPoint(e.Location);
            if ((idx >= 0) && (idx != m_suggestionList.SelectedIndex))
            {
                m_suggestionList.SelectedIndex = idx;
            }
        }
        #endregion

        #region owner drawn
        /// <summary>
        /// We keep track of system settings changes for the font
        /// </summary>
        private void onFontChanged(object sender, EventArgs e)
        {
            if (m_boldFont != null)
            {
                m_boldFont.Dispose();
            }
            m_suggestionList.Font = Font;
            m_boldFont = new Font(Font, FontStyle.Bold);
            m_suggestionList.ItemHeight = m_boldFont.Height + 2;
        }

        /// <summary>
        /// Draw a segment of a string and updates the bound rectangle for being used for the next segment drawing
        /// </summary>
        private static void DrawString(Graphics g, Color color, ref Rectangle rect, string text, Font font)
        {
            Size proposedSize = new Size(int.MaxValue, int.MaxValue);
            Size sz = TextRenderer.MeasureText(g, text, font, proposedSize, TextFormatFlags.NoPadding);
            TextRenderer.DrawText(g, text, font, rect, color, TextFormatFlags.Left | TextFormatFlags.VerticalCenter | TextFormatFlags.NoPadding | TextFormatFlags.NoPrefix);
            rect.X += sz.Width;
            rect.Width -= sz.Width;
        }

        /// <summary>
        /// Draw an item in the suggestion listbox
        /// </summary>
        private void onSuggestionListDrawItem(object sender, DrawItemEventArgs e)
        {
            StringMatch sm = (StringMatch) m_suggestionList.Items[e.Index];

            e.DrawBackground();
            
            bool isBold = sm.StartsOnMatch;
            Rectangle rBounds = e.Bounds;

            foreach (string s in sm.Segments)
            {
                Font f = isBold ? m_boldFont : Font;
                DrawString(e.Graphics, e.ForeColor, ref rBounds, s, f);
                isBold = !isBold;
            }

            e.DrawFocusRectangle();
        }
        #endregion
        
        #region misc
        [Category("Behavior"), DefaultValue(false), Description("Specifies whether items in the list portion of the combobo are sorted.")]
        public new bool Sorted
        {
            get { return base.Sorted; }
            set
            {
                m_suggestionList.Sorted = value;
                base.Sorted = value;
            }
        }

        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        public new bool DroppedDown
        {
            get { return base.DroppedDown || m_dropDown.Visible; }
            set 
            { 
                m_dropDown.Visible = false;
                base.DroppedDown = value;
            }
        }
        #endregion

        #region New properties
        [
            DefaultValue(StringMatchingMethod.NoWildcards),
            Description("How strings are matched against the user input"),
            Browsable(true),
            EditorBrowsable(EditorBrowsableState.Always),
            Category("Behavior")
        ]
        public StringMatchingMethod MatchingMethod
        {
            get { return m_matchingMethod;  }
            set
            {
                if (m_matchingMethod != value)
                {
                    m_matchingMethod = value;
                    if (m_dropDown.Visible)
                    {
                        // recalculate the matches
                        showDropDown();
                    }
                }
            }
        }
        #endregion
        
        #region Hidden inherited properties
        /// <summary>This property is not relevant for this class.</summary>
        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)]
        public new AutoCompleteSource AutoCompleteSource
        {
            get { return base.AutoCompleteSource; }
            set { base.AutoCompleteSource = value; }
        }
        /// <summary>This property is not relevant for this class.</summary>
        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)]
        public new AutoCompleteStringCollection AutoCompleteCustomSource 
        {
            get { return base.AutoCompleteCustomSource; }
            set { base.AutoCompleteCustomSource = value; }
        }
        /// <summary>This property is not relevant for this class.</summary>
        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)]
        public new AutoCompleteMode AutoCompleteMode
        {
            get { return base.AutoCompleteMode; }
            set { base.AutoCompleteMode = value; }
        }
        /// <summary>This property is not relevant for this class.</summary>
        [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)]
        public new ComboBoxStyle DropDownStyle
        {
            get { return base.DropDownStyle; }
            set { base.DropDownStyle = value; }
        }
        #endregion
    }
}

using System.Diagnostics;
using System.Drawing;
using System.Windows.Forms;
using SergeUtils;

namespace TestCombo
{
    public partial class Form1 : Form
    {
        private static readonly object[] s_NOBELS_LITTERATURE =
        {
            "Albert Camus",
            "Aleksandr Isayevich Solzhenitsyn",
            "Alice Munro",
            "Anatole France",
            "André Paul Guillaume Gide",
            "Bjørnstjerne Martinus Bjørnson",
            "Boris Leonidovich Pasternak",
            "Carl Friedrich Georg Spitteler",
            "Carl Gustaf Verner von Heidenstam",
            "Christian Matthias Theodor Mommsen",
            "Count Maurice (Mooris) Polidore Marie Bernhard Maeterlinck",
            "Czeslaw Milosz",
            "Dario Fo",
            "Derek Walcott",
            "Doris Lessing",
            "Earl (Bertrand Arthur William) Russell",
            "Elfriede Jelinek",
            "Elias Canetti",
            "Erik Axel Karlfeldt",
            "Ernest Miller Hemingway",
            "Eugene Gladstone O'Neill",
            "Eugenio Montale",
            "Eyvind Johnson",
            "François Mauriac",
            "Frans Eemil Sillanpää",
            "Frédéric Mistral",
            "Gabriel García Márquez",
            "Gabriela Mistral",
            "Gao Xingjian",
            "George Bernard Shaw",
            "George Elliot",
            "Gerhart Johann Robert Hauptmann",
            "Giorgos Seferis",
            "Giosuè Carducci",
            "Grazia Deledda",
            "Günter Grass",
            "Halldór Kiljan Laxness",
            "Harry Martinson",
            "Harold Pinter",
            "Heinrich Böll",
            "Henri Bergson",
            "Henrik Pontoppidan",
            "Henryk Sienkiewicz",
            "Hermann Hesse",
            "Herta Müller",
            "Iain Banks",
            "Imre Kertész",
            "Isaac Bashevis Singer",
            "Ivan Alekseyevich Bunin",
            "Ivo Andric",
            "Jacinto Benavente",
            "Jean-Marie Gustave Le Clézio",
            "Jean-Paul Sartre",
            "Johannes Vilhelm Jensen",
            "John Galsworthy",
            "John M. Coetzee",
            "John Steinbeck",
            "José Echegaray y Eizaguirre",
            "José Saramago",
            "Joseph Brodsky",
            "Juan Ramón Jiménez",
            "Karl Adolph Gjellerup",
            "Kenzaburo Oe",
            "Knut Pedersen Hamsun",
            "Luigi Pirandello",
            "Mario Vargas Llosa",
            "Miguel Angel Asturias",
            "Mikhail Aleksandrovich Sholokhov",
            "Mo Yan",
            "Nadine Gordimer",
            "Naguib Mahfouz",
            "Nelly Sachs",
            "Octavio Paz",
            "Odysseus Elytis",
            "Orhan Pamuk",
            "Pablo Neruda",
            "Pär Fabian Lagerkvist",
            "Patrick White",
            "Paul Johann Ludwig Heyse",
            "Pearl Buck",
            "Rabindranath Tagore",
            "Roger Martin du Gard",
            "Romain Rolland",
            "Rudolf Christoph Eucken",
            "Rudyard Kipling",
            "Saint-John Perse",
            "Salman Rushdie",
            "Salvatore Quasimodo",
            "Samuel Beckett",
            "Saul Bellow",
            "Seamus Heaney",
            "Selma Ottilia Lovisa Lagerlöf",
            "Shmuel Yosef Agnon",
            "Sinclair Lewis",
            "Sir Vidiadhar Surajprasad Naipaul",
            "Sir Winston Leonard Spencer Churchill",
            "Sully Prudhomme",
            "Thomas Stearns Eliot",
            "Tomas Tranströmer",
            "Toni Morrison",
            "Yasunari Kawabata",
            "Valerie Martin",
            "Vicente Aleixandre",
            "William Faulkner",
            "Wislawa Szymborska",
            "Wole Soyinka",
            "Thomas Mann",
            "Sigrid Undset",
            "Wladyslaw Stanislaw Reymont",
            "William Butler Yeats",
        };

        public class MethodItem
        {
            public string Name { get; set; }
            public StringMatchingMethod Value { get; set; }
        }

        public Form1()
        {
            InitializeComponent();

            m_combo.Items.Add("EBSAntiJitterConfig");
            m_combo.Items.Add("BridgeFilterConfig2");
            m_combo.Items.Add("PCMActiveUserList");
            m_combo.Items.Add("SpotFXPriceConfigIDList");
            m_combo.Items.AddRange(s_NOBELS_LITTERATURE);

            m_methodCB.DisplayMember = "Name";
            m_methodCB.Items.Add(new MethodItem { Name = "No wildcards", Value = StringMatchingMethod.NoWildcards });
            m_methodCB.Items.Add(new MethodItem { Name = "Use wildcards", Value = StringMatchingMethod.UseWildcards });
            m_methodCB.Items.Add(new MethodItem { Name = "Use regexs", Value = StringMatchingMethod.UseRegexs });
            m_methodCB.SelectedIndex = 0;

            m_combo.MatchingMethod = StringMatchingMethod.NoWildcards;

            Font = new Font("Segoe UI", 9.0f);

        }

        private void onKeyDown(object sender, KeyEventArgs e)
        {
            Debug.WriteLine("key down {0}", ActiveControl.GetType().Name);
        }

        private void onSelectionChanged(object sender, System.EventArgs e)
        {
            m_label.Text = string.Format("Selection: '{0}'", m_combo.SelectedItem);
        }

        private void onMethodChanged(object sender, System.EventArgs e)
        {
            MethodItem mi = (MethodItem) m_methodCB.SelectedItem;
            m_combo.MatchingMethod = mi.Value;
        }
    }
}