Autocomplete Menu - CodeProject


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We all use VisualStudio's autocomplete menu, aka IntelliSense. This is very useful, is not it? Unfortunately, .NET FW does not contain built-in component for autocomplete menu. The proposed control fills this gap.

AutocompleteMenu allows you to easily embed a drop-down hints into any TextBox or RichTextBox on your form.


The component contains several classes. Below summarizes the main classes and their functions:

AutocompleteMenu - main component of which contains the basic functions. It subscribes to the events of TextBox, looks for suitable variants, shows a drop-down menu and inserts new text into textbox.

Below are basic properties of the AutocompleteMenu:

  • AllowTabKey - Allows TAB for select menu item.
  • AppearInterval - Interval of menu appear (ms).
  • ImageList - Image list used for items.
  • Items - list of text of menu items (simplest variant of usage of AutocompleteMenu).
  • MaximumSize - Maximum size of popup menu.
  • MinFragmentLength - Minimum fragment length for menu appearing. AutocompleteMenu appears only if current fragment around caret has no less then MinFragmentLength symbols.
  • SearchPattern - Regex pattern for serach fragment around caret.

AutocompleteMenuHost - visual component that derived from ToolStripDropDown. This control allows you to display the menu without losing focus on the main form.

AutocompleteListView - visual component that inherited from UserControl. With GDI+, it draws the items of the drop-down menu. This component is similar to ListView but it allows you to display a large number of elements with a good performance.

AutocompleteItem - menu item. This class contains all the necessary information about menu item. You can extend menu features, inheriting your elements from AutocompleteItem and overriding its virtual methods. Below are basic properties of AutocompleteItem:

  • Text - text for inserting into textbox.
  • MenuText - this text will displayed in popup menu.
  • ImageIndex - index of image for this item.
  • ToolTipTitle - title for tooltip. If ToolTipTitle is null, tooltip will not appear for this item.
  • ToolTipText - text of tooltip.
  • Tag - you can store any data here.

Below are some methods you can override:

  • GetTextForReplace - returns inserting text. You can dynamically change inserting text. For example, you can insert current date.
  • Compare - this method defines will this item visible in menu or not. By default this method make visible only items begin with given fragment. But you can override this behaviour. For example, you can compare by substring, or make fuzzy comparison.
  • OnSelected - this method is called when text was inserted in textbox. You can make here some additional operations with text. For example, you can move caret into some position.

The library also contains a few useful classes derived from AutocompleteItem: SnippetAutocompleteItem (can be used for inserting of code snippets), MethodAutocompleteItem (can be used for inserting of method name after dot), SubstringAutocompleteItem (compares text by substring), MulticolumnAutocompleteItem (draws multicolumn menu).

Using the code

Easy usage:

1) Throw AutocompleteMenu component on your form.

2) Type text of the menu items in AutocompleteMenu.Items:


3) Set the AutocompleteMenu property of your TextBox:

4) That's all folks Smile | :)

Advanced usage:

1) Throw AutocompleteMenu component on your form.

2) Create a list of items, and add to the menu, using the methods SetAutocompleteItems() or AddItem(). For example:

string[] snippets = { "if(^)\n{\n}", "if(^)\n{\n}\nelse\n{\n}", "for(^;;)\n{\n}", "while(^)\n{\n}", "do${\n^}while();", "switch(^)\n{\n\tcase : break;\n}" };

private void BuildAutocompleteMenu()
    var items = new List<AutocompleteItem>();

    foreach (var item in snippets)
        items.Add(new SnippetAutocompleteItem(item) { ImageIndex = 1 });

    //set as autocomplete source

Also, you can add own items, inherited from AutocompleteItem. For example:

internal class EmailSnippet : AutocompleteItem
    public EmailSnippet(string email): base(email)
        ImageIndex = 0;
        ToolTipTitle = "Insert email:";
        ToolTipText = email;

    public override CompareResult Compare(string fragmentText)
        if (fragmentText == Text)
            return CompareResult.VisibleAndSelected;
        if (fragmentText.Contains("@"))
            return CompareResult.Visible;
        return CompareResult.Hidden;

More details see the example AdvancedSample of demo application.


You can use following shortcuts:

  • Ctrl+Space - forcibly opens AutocompleteMenu.
  • Up, Down, PgUp, PgDown - navigates across menu.
  • Enter, Tab, DblClick on the item - inserts selected item into text (Tab works only if AllowTabKey is true).
  • Esc - closes menu.

Note that these keys are working, despite the fact that the focus is in the textbox.

Item's tooltip appears if you click on the item.

Custom ListView

You can use the custom controls for displaying AutocompleteMenu (like ListView, ListBox, DataGridView, TreeView, etc). For this, create own control (derived from Control) and implement interface IAutocompleteListView. More details see in CustomListViewSample.

Dynamic context menu

It is frequently necessary that the menu display not a fixed set of items, but was changing dynamically, depending on the text. This task can be solved.

Note that method SetAutocompleteItems() of menu takes IEnumerable as collection of displayed items.

So, you can do not generate a list of items at the start of the program, and generate it dynamically at the time of the call the enumerator from the menu.

The following code demonstrates this idea:

autocompleteMenu1.SetAutocompleteItems(new DynamicCollection(tb));

internal class DynamicCollection : IEnumerable<AutocompleteItem>
    public IEnumerator<AutocompleteItem> GetEnumerator()
        return BuildList().GetEnumerator();

    private IEnumerable<AutocompleteItem> BuildList()
        //find all words of the text
        var words = new Dictionary<string, string>();
        foreach (Match m in Regex.Matches(tb.Text, @"\b\w+\b"))
            words[m.Value] = m.Value;

        //return autocomplete items
        foreach(var word in words.Keys)
            yield return new AutocompleteItem(word);

Fully implemented sample see in DynamicMenuSample.


Autocomplete menu is compatible with TextBox, RichTextBox, MaskedTextBox, FastColoredTextBox[^] and other controls derived from TextBoxBase.

Also, Autocomplete Menu is compatible with any control supports following properties and methods:

  • string SelectedText{get;set;}
  • int SelectionLength{get;set;}
  • int SelectionStart{get;set;}
  • Point GetPositionFromCharIndex(int charPos)

Even if your control do not support these methods, you can create own wrapper for it. For this, you must create own wrapper class and implement there interface ITextBoxWrapper.

Below described methods and properties of ITextBoxWrapper:

public interface ITextBoxWrapper
    Control TargetControl { get; }
    string Text { get; }
    string SelectedText { get; set; }
    int SelectionLength { get; set; }
    int SelectionStart { get; set; }
    Point GetPositionFromCharIndex(int pos);
    event EventHandler LostFocus;
    event ScrollEventHandler Scroll;
    event KeyEventHandler KeyDown;
    event MouseEventHandler MouseDown;

So, when you made wrapper you can simply attach AutocompleteMenu to your control. Something like this:

public partial class Form1 : Form
    public Form1()

    //attach myControl1 to autocompleteMenu1
        autocompleteMenu1.TargetControlWrapper = new MyControlWrapper(myControl1);

internal class MyControlWrapper : ITextBoxWrapper
    private MyControl tb;

    public MyControlWrapper(MyControl tb)
        this.tb = tb;

//here we implement ITextBoxWrapper


Demo application contains several samples:

SimplestSample - shows how to use the control by simplest way.

CustomItemSample - shows how to create own class derived from AutocompleteItem.

AdvancedSample - shows how to create custom autocomplete menu with keywords, snippets, method suggestions, text correctors etc.

ExtraLargeSample - demonstrates performance of the component with extra large list of menu items (one million).

ComboboxSample - shows how to create analog of Combobox, but with very large dropdown list and with searching by substring.

MulticolumnSample - shows how to make multicolumn autocomplete menu:

CustomListViewSample - shows how to make custom ListView, hosted in autocomplete menu:

DynamicMenuSample - this example shows how to create dynamic context-sensitive autocomplete menu.

DataGridViewSample - shows how to attach AutocompleteMenu to DataGridView:


13 Apr 2012 - First release.

21 Apr 2012 - The control is refactored. Added support of the FastColoredTextBox[^] and other controls.

9 May 2012 - The control is refactored. Some samples were added.

3 Dec 2014 - Property Colors was added.

8 Feb 2015 - Small bugs were fixed.

19 Mar 2015 - Small bugs were fixed.