WinForms | C# | AutoComplete in the Middle of a Textbox?

Question

I have a textbox that does autocompletion like so:

txtName.AutoCompleteMode = AutoCompleteMode.Suggest; txtName.AutoCompleteSource = AutoCompleteSource.CustomSource; txtName.AutoCompleteCustomSource = namesCollection; 

It works, but only at the beginning of a textbox. I'd like autocomplete to kick in for any word the user is entering, at any position in the textbox.

Answer 1

using System; using System.Collections.Generic; using System.Drawing; using System.Windows.Forms;  namespace TubeUploader {     public class AutoCompleteTextBox : TextBox     {         private ListBox _listBox;         private bool _isAdded;         private String[] _values;         private String _formerValue = String.Empty;          public AutoCompleteTextBox()         {             InitializeComponent();             ResetListBox();         }          private void InitializeComponent()         {             _listBox = new ListBox();             KeyDown += this_KeyDown;             KeyUp += this_KeyUp;         }          private void ShowListBox()         {             if (!_isAdded)             {                 Parent.Controls.Add(_listBox);                 _listBox.Left = Left;                 _listBox.Top = Top + Height;                 _isAdded = true;             }             _listBox.Visible = true;             _listBox.BringToFront();         }          private void ResetListBox()         {             _listBox.Visible = false;         }          private void this_KeyUp(object sender, KeyEventArgs e)         {             UpdateListBox();         }          private void this_KeyDown(object sender, KeyEventArgs e)         {             switch (e.KeyCode)             {                 case Keys.Tab:                     {                         if (_listBox.Visible)                         {                             InsertWord((String)_listBox.SelectedItem);                             ResetListBox();                             _formerValue = Text;                         }                         break;                     }                 case Keys.Down:                     {                         if ((_listBox.Visible) && (_listBox.SelectedIndex < _listBox.Items.Count - 1))                             _listBox.SelectedIndex++;                          break;                     }                 case Keys.Up:                     {                         if ((_listBox.Visible) && (_listBox.SelectedIndex > 0))                             _listBox.SelectedIndex--;                          break;                     }             }         }          protected override bool IsInputKey(Keys keyData)         {             switch (keyData)             {                 case Keys.Tab:                     return true;                 default:                     return base.IsInputKey(keyData);             }         }          private void UpdateListBox()         {             if (Text == _formerValue) return;             _formerValue = Text;             String word = GetWord();              if (_values != null && word.Length > 0)             {                 String[] matches = Array.FindAll(_values,                                                  x => (x.StartsWith(word, StringComparison.OrdinalIgnoreCase) && !SelectedValues.Contains(x)));                 if (matches.Length > 0)                 {                     ShowListBox();                     _listBox.Items.Clear();                     Array.ForEach(matches, x => _listBox.Items.Add(x));                     _listBox.SelectedIndex = 0;                     _listBox.Height = 0;                     _listBox.Width = 0;                     Focus();                     using (Graphics graphics = _listBox.CreateGraphics())                     {                         for (int i = 0; i < _listBox.Items.Count; i++)                         {                             _listBox.Height += _listBox.GetItemHeight(i);                             // it item width is larger than the current one                             // set it to the new max item width                             // GetItemRectangle does not work for me                             // we add a little extra space by using '_'                             int itemWidth = (int)graphics.MeasureString(((String)_listBox.Items[i]) + "_", _listBox.Font).Width;                             _listBox.Width = (_listBox.Width < itemWidth) ? itemWidth : _listBox.Width;                         }                     }                 }                 else                 {                     ResetListBox();                 }             }             else             {                 ResetListBox();             }         }          private String GetWord()         {             String text = Text;             int pos = SelectionStart;              int posStart = text.LastIndexOf(' ', (pos < 1) ? 0 : pos - 1);             posStart = (posStart == -1) ? 0 : posStart + 1;             int posEnd = text.IndexOf(' ', pos);             posEnd = (posEnd == -1) ? text.Length : posEnd;              int length = ((posEnd - posStart) < 0) ? 0 : posEnd - posStart;              return text.Substring(posStart, length);         }          private void InsertWord(String newTag)         {             String text = Text;             int pos = SelectionStart;              int posStart = text.LastIndexOf(' ', (pos < 1) ? 0 : pos - 1);             posStart = (posStart == -1) ? 0 : posStart + 1;             int posEnd = text.IndexOf(' ', pos);              String firstPart = text.Substring(0, posStart) + newTag;             String updatedText = firstPart + ((posEnd == -1) ? "" : text.Substring(posEnd, text.Length - posEnd));               Text = updatedText;             SelectionStart = firstPart.Length;         }          public String[] Values         {             get             {                 return _values;             }             set             {                 _values = value;             }         }          public List<String> SelectedValues         {             get             {                 String[] result = Text.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);                 return new List<String>(result);             }         }      }  } 

Sample Usage

using System; using System.Windows.Forms;  namespace AutoComplete {     public partial class TestForm : Form     {         private readonly String[] _values = { "one", "two", "three", "tree", "four", "fivee" };          public TestForm()         {             InitializeComponent();             // AutoComplete is our special textbox control on the form             AutoComplete.Values = _values;         }      } }