C winforms combobox dynamic autocomplete

Question

My problem is similar to this one  How can I dynamically change auto complete entries in a C  combobox or textbox  But I still don t find solution   The problem briefly   I have an ComboBox and a large number of records to show in it  When user starts typing I want to load records that starts with input text and offer the user for autocomplete   As described in the topic above I can t load them on  omboBox TextChanged because I always overwrite the previous results and never see them   Can I implement this using only ComboBox   not TextBox or ListBox   I use this settings    omboBox AutoCompleteMode   AutoCompleteMode SuggestAppend   omboBox AutoCompleteSource   AutoCompleteSource CustomSource

User · Answer

I wrote something like this       private void frmMain Load object sender  EventArgs e        cboFromCurrency Items Clear        cboComboBox1 AutoCompleteMode   AutoCompleteMode Suggest      cboComboBox1 AutoCompleteSource   AutoCompleteSource ListItems         Load data in comboBox   gt  cboComboBox1 DataSource                Other things    private void cboComboBox1 KeyPress object sender  KeyPressEventArgs e        cboComboBox1 DroppedDown   false      That s all  Y

User · Answer

Yes  you surely can    but it needs some work to make it work seamlessly  This is some code I came up with  Bear in mind that it does not use combobox s auto-complete features  and it might be quite slow if you use it to sift thru a lot of items      string   data   new string          Absecon   Abstracta   Abundantia   Academia   Acadiau   Acamas        Ackerman   Ackley   Ackworth   Acomita   Aconcagua   Acton   Acushnet        Acworth   Ada   Ada   Adair   Adairs   Adair   Adak   Adalberta   Adamkrafft        Adams      public Form1         InitializeComponent       private void comboBox1 TextChanged object sender  EventArgs e        HandleTextChanged       private void HandleTextChanged         var txt   comboBox1 Text      var list   from d in data                where d ToUpper   StartsWith comboBox1 Text ToUpper                   select d      if  list Count    gt  0                comboBox1 DataSource   list ToList              comboBox1 SelectedIndex   0          var sText   comboBox1 Items 0  ToString            comboBox1 SelectionStart   txt Length          comboBox1 SelectionLength   sText Length - txt Length          comboBox1 DroppedDown   true          return            else               comboBox1 DroppedDown   false          comboBox1 SelectionStart   txt Length           private void comboBox1 KeyUp object sender  KeyEventArgs e        if  e KeyCode    Keys Back                int sStart   comboBox1 SelectionStart          if  sStart  gt  0                        sStart--              if  sStart    0                                comboBox1 Text                                 else                               comboBox1 Text   comboBox1 Text Substring 0  sStart                                   e Handled   true

User · Answer

using  var client   new UserServicesClient            var list   new AutoCompleteStringCollection         list AddRange client ListNames query  ToArray          comboBoxName AutoCompleteCustomSource   list

User · Answer

Here is my final solution  It works fine with a large amount of data  I use Timer to make sure the user want find current value  It looks like complex but it doesn t  Thanks to Max Lambertini for the idea           private bool  canUpdate   true            private bool  needUpdate   false                    If text has been changed then start timer           If the user doesn t change text while the timer runs then start search         private void combobox1 TextChanged object sender  EventArgs e                        if   needUpdate                                if   canUpdate                                         canUpdate   false                      UpdateData                                                         else                                       RestartTimer                                                       private void UpdateData                         if  combobox1 Text Length  gt  1                                List lt string gt  searchData   Search GetData combobox1 Text                   HandleTextChanged searchData                                             If an item was selected don t start new search         private void combobox1 SelectedIndexChanged object sender  EventArgs e                         needUpdate   false                       Update data only when the user  not program  change something         private void combobox1 TextUpdate object sender  EventArgs e                         needUpdate   true                       While timer is running don t start search           timer1 Interval   1500          private void RestartTimer                         timer1 Stop                 canUpdate   false              timer1 Start                         Update data when timer stops         private void timer1 Tick object sender  EventArgs e                         canUpdate   true              timer1 Stop                UpdateData                         Update combobox with new data         private void HandleTextChanged List lt string gt  dataSource                        var text   combobox1 Text               if  dataSource Count    gt  0                                combobox1 DataSource   dataSource                     var sText   combobox1 Items 0  ToString                    combobox1 SelectionStart   text Length                  combobox1 SelectionLength   sText Length - text Length                  combobox1 DroppedDown   true                    return                            else                               combobox1 DroppedDown   false                  combobox1 SelectionStart   text Length                            This solution isn t very cool  So if someone has another solution please share it with me

User · Answer

In previous replies are drawbacks  Offers its own version with the selection in the drop down list the desired item       private ConnectSqlForm                 InitializeComponent            cmbDatabases TextChanged    UpdateAutoCompleteComboBox          cmbDatabases KeyDown    AutoCompleteComboBoxKeyPress             private void UpdateAutoCompleteComboBox object sender  EventArgs e                var comboBox   sender as ComboBox          if comboBox    null          return          string txt   comboBox Text          string foundItem   String Empty          foreach string item in comboBox Items              if   String IsNullOrEmpty txt   amp  amp  item ToLower   StartsWith txt ToLower                                   foundItem   item                  break                         if   String IsNullOrEmpty foundItem                         if  String IsNullOrEmpty txt      txt Equals foundItem                                 comboBox TextChanged -  UpdateAutoCompleteComboBox                  comboBox Text   foundItem                  comboBox DroppedDown   true                  Cursor Current   Cursors Default                  comboBox TextChanged    UpdateAutoCompleteComboBox                             comboBox SelectionStart   txt Length              comboBox SelectionLength   foundItem Length - txt Length                    else             comboBox DroppedDown   false             private void AutoCompleteComboBoxKeyPress object sender  KeyEventArgs e                var comboBox   sender as ComboBox          if  comboBox    null  amp  amp  comboBox DroppedDown                        switch  e KeyCode                                case Keys Back                      int sStart   comboBox SelectionStart                      if  sStart  gt  0                                                sStart--                          comboBox Text   sStart    0        comboBox Text Substring 0  sStart                                             e SuppressKeyPress   true                      break

User · Answer

I Also come across these kind of requirements recently I set the below properties with out writing the code it works see if this helps you

User · Answer

This was a major pain to get working   I hit a bunch of dead ends  but the final result is reasonably straight forward   Hopefully it can be of benefit to someone  It may need a little spit and polish that s all   Note   addressFinder CompleteAsync returns a list of KeyValuePairs   public partial class MyForm   Form       private readonly AddressFinder  addressFinder      private readonly AddressSuggestionsUpdatedEventHandler  addressSuggestionsUpdated       private delegate void AddressSuggestionsUpdatedEventHandler object sender  AddressSuggestionsUpdatedEventArgs e        public MyForm                 InitializeComponent              addressFinder   new AddressFinder new AddressFinderConfigurationProvider               addressSuggestionsUpdated    AddressSuggestions Updated           MyComboBox DropDownStyle   ComboBoxStyle DropDown          MyComboBox DisplayMember    Value           MyComboBox ValueMember    Key              private void MyComboBox KeyPress object sender  KeyPressEventArgs e                if  char IsControl e KeyChar                         return                     var searchString   ThreadingHelpers GetText MyComboBox            if  searchString Length  gt  1                        Task Run      gt  GetAddressSuggestions searchString                         private async Task GetAddressSuggestions string searchString                var addressSuggestions   await  addressFinder CompleteAsync searchString  ConfigureAwait false            if   addressSuggestionsUpdated IsNotNull                           addressSuggestionsUpdated Invoke this  new AddressSuggestionsUpdatedEventArgs addressSuggestions                         private void AddressSuggestions Updated object sender  AddressSuggestionsUpdatedEventArgs eventArgs                try                       ThreadingHelpers BeginUpdate MyComboBox                var text   ThreadingHelpers GetText MyComboBox                ThreadingHelpers ClearItems MyComboBox                foreach  var addressSuggestions in eventArgs AddressSuggestions                                ThreadingHelpers AddItem MyComboBox  addressSuggestions                              ThreadingHelpers SetDroppedDown MyComboBox  true                ThreadingHelpers ClearSelection MyComboBox               ThreadingHelpers SetText MyComboBox  text               ThreadingHelpers SetSelectionStart MyComboBox  text Length                     catch  Exception ex                        Console WriteLine ex                     finally                       ThreadingHelpers EndUpdate MyComboBox                        private class AddressSuggestionsUpdatedEventArgs   EventArgs               public IList lt KeyValuePair lt string  string gt  gt  AddressSuggestions   get  private set             public AddressSuggestionsUpdatedEventArgs IList lt KeyValuePair lt string  string gt  gt  addressSuggestions                        AddressSuggestions   addressSuggestions                      ThreadingHelpers is just a set of static methods of the form       public static string GetText ComboBox comboBox                if  comboBox InvokeRequired                        return  string comboBox Invoke new Func lt string gt       gt  GetText comboBox                        lock  comboBox                        return comboBox Text                       public static void SetText ComboBox comboBox  string text                if  comboBox InvokeRequired                        comboBox Invoke new Action      gt  SetText comboBox  text                 return                     lock  comboBox                        comboBox Text   text

User · Answer

I ve found Max Lambertini s answer very helpful  but have modified his HandleTextChanged method as such         I like min length set to 3  to not give too many options        after the first character or two the user types     public Int32 AutoCompleteMinLength  get  set        private void HandleTextChanged             var txt   comboBox Text          if  txt Length  lt  AutoCompleteMinLength              return             The GetMatches method can be whatever you need to filter            table rows or some other data source based on the typed text          var matches   GetMatches comboBox Text ToUpper              if  matches Count    gt  0                  The inside of this if block has been changed to allow               users to continue typing after the auto-complete results               are found              comboBox Items Clear                comboBox Items AddRange matches               comboBox DroppedDown   true              Cursor Current   Cursors Default              comboBox Select txt Length  0               return                    else               comboBox DroppedDown   false              comboBox SelectionStart   txt Length

User · Answer

Take 2   My answer below didn t get me all the way to the desired result  but it may still be useful to somebody   The auto-select feature of the ComboBox was causing me major pain   This one uses a TextBox sitting over the top of a ComboBox  allowing me to ignore whatever appears in the ComboBox itself and just respond to the selection changed event    Create Form Add ComboBox   Set desired size and location Set DropDownStyle to DropDown Set TabStop to false Set DisplayMember to Value  I m using a list of KeyValuePairs  Set ValueMember to Key  Add Panel   Set to same size as ComboBox Cover ComboBox with the Panel  This accounts for the standard ComboBox being taller than the standard TextBox   Add TextBox   Place TextBox over the top of the Panel Align bottom of the TextBox with the bottom of Panel ComboBox    Code behind  public partial class TestForm   Form          Custom class for managing calls to an external address finder service     private readonly AddressFinder  addressFinder          Events for handling async calls to address finder service     private readonly AddressSuggestionsUpdatedEventHandler  addressSuggestionsUpdated      private delegate void AddressSuggestionsUpdatedEventHandler object sender  AddressSuggestionsUpdatedEventArgs e        public TestForm                 InitializeComponent              addressFinder   new AddressFinder new AddressFinderConfigurationProvider              addressSuggestionsUpdated    AddressSuggestions Updated             private void textBox1 PreviewKeyDown object sender  PreviewKeyDownEventArgs e                if  e KeyCode    Keys Tab                        comboBox1 SelectionChangeCommitted sender  e               comboBox1 DroppedDown   false                       private void textBox1 KeyDown object sender  KeyEventArgs e                if  e KeyCode    Keys Up                        if  comboBox1 Items Count  gt  0                                if  comboBox1 SelectedIndex  gt  0                                        comboBox1 SelectedIndex--                                               e Handled   true                    else if  e KeyCode    Keys Down                        if  comboBox1 Items Count  gt  0                                if  comboBox1 SelectedIndex  lt  comboBox1 Items Count - 1                                        comboBox1 SelectedIndex                                                 e Handled   true                    else if  e KeyCode    Keys Enter                        comboBox1 SelectionChangeCommitted sender  e               comboBox1 DroppedDown   false               textBox1 SelectionStart   textBox1 TextLength               e Handled   true                       private void textBox1 KeyPress object sender  KeyPressEventArgs e                if  e KeyChar      r       Enter key                       e Handled   true              return                     if  char IsControl e KeyChar   amp  amp  e KeyChar      b      Backspace key                       return                     if  textBox1 Text Length  gt  1                        Task Run      gt  GetAddressSuggestions textBox1 Text                         private void comboBox1 SelectionChangeCommitted object sender  EventArgs e                if  comboBox1 Items Count  gt  0  amp  amp              comboBox1 SelectedItem IsNotNull    amp  amp              comboBox1 SelectedItem is KeyValuePair lt string  string gt                         var selectedItem    KeyValuePair lt string  string gt  comboBox1 SelectedItem               textBox1 Text   selectedItem Value                  Do Work with selectedItem                      private async Task GetAddressSuggestions string searchString                var addressSuggestions   await  addressFinder CompleteAsync searchString  ConfigureAwait false            if   addressSuggestionsUpdated IsNotNull                           addressSuggestionsUpdated Invoke this  new AddressSuggestionsUpdatedEventArgs addressSuggestions                         private void AddressSuggestions Updated object sender  AddressSuggestionsUpdatedEventArgs eventArgs                try                       ThreadingHelper BeginUpdate comboBox1                ThreadingHelper ClearItems comboBox1                if  eventArgs AddressSuggestions Count  gt  0                                foreach  var addressSuggestion in eventArgs AddressSuggestions                                        var item   new KeyValuePair lt string  string gt  addressSuggestion Key  addressSuggestion Value ToUpper                         ThreadingHelper AddItem comboBox1  item                                      ThreadingHelper SetDroppedDown comboBox1  true                   ThreadingHelper SetVisible comboBox1  true                             else                               ThreadingHelper SetDroppedDown comboBox1  false                                   finally                       ThreadingHelper EndUpdate comboBox1                        private class AddressSuggestionsUpdatedEventArgs   EventArgs               public IList lt KeyValuePair lt string  string gt  gt  AddressSuggestions   get             public AddressSuggestionsUpdatedEventArgs IList lt KeyValuePair lt string  string gt  gt  addressSuggestions                        AddressSuggestions   addressSuggestions                      You may or may not have issues with setting the DroppedDown property of the ComboBox   I eventually just wrapped it up in a try block with an empty catch block   Not a great solution  but it works   Please see my other answer below for info on ThreadingHelpers   Enjoy

User · Answer

This code is write on your form load  It display all the Tour in database when user type letter in combo box  This code automatically suggest and append the right choice as user want                con Open                cmd   new SqlCommand  SELECT DISTINCT Tour FROM DetailsTB   con               SqlDataReader sdr   cmd ExecuteReader                DataTable dt   new DataTable                dt Load sdr               combo search2 DisplayMember    Tour               combo search2 DroppedDown   true               List lt string gt  list   new List lt string gt                 foreach  DataRow row in dt Rows                                list Add row Field lt string gt   Tour                               this combo search2 Items AddRange list ToArray lt string gt                  combo search2 AutoCompleteMode   AutoCompleteMode SuggestAppend              combo search2 AutoCompleteSource   AutoCompleteSource ListItems              con Close

[c#] C# winforms combobox dynamic autocomplete

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