Combo List Cell

ComboListCell creates an editable combo box cell: users can type freely, rely on auto-completion, or pick from a drop-down list. Compared to DropdownListCell, it keeps the suggestions but also accepts new values. Examples below assume standard namespaces (e.g., System.Collections.Generic, System.Linq) are in scope when lists are used.

Create a combo list cell

using unvell.ReoGrid;
using unvell.ReoGrid.CellTypes;

var sheet = grid.CurrentWorksheet;
var combo = new ComboListCell(new[] { "Apple", "Banana", "Orange", "Applause", "Appreciate" });
sheet.Cells["C3"].Body = combo;

Populate options later by keeping a mutable list and passing it in:

var items = new List<string> { "Alpha", "Beta", "Gamma" };
var combo = new ComboListCell(items);
items.Add("Delta"); // the list stays linked to the cell
sheet["B5"] = combo;

You can also bind to a range so the list reflects cell contents:

var range = new ReferenceRange(sheet, new RangePosition("A2:A20"));
sheet["D2"] = new ComboListCell(range);

Auto completion

Auto completion is enabled by default. Disable it if you only want manual typing or the drop-down:

combo.EnableAutoCompletion = false;

Provide custom matching logic (default is case-insensitive prefix match). Returning true keeps the item in the suggestion list and lets ReoGrid append the remaining characters when the user types:

combo.AutoCompleteComparerator = (item, text) =>
{
    if (string.IsNullOrWhiteSpace(text)) return false;
    return item.Contains(text, StringComparison.OrdinalIgnoreCase); // substring match
};

For large or remote data sets, supply your own search provider. It is invoked during typing; return the items that should appear in the drop-down for the current text:

combo.CandidationListSearchProvider = text =>
{
    return ProductSearch(text?.ToString())
        .Take(20)
        .ToList();
};

Handle selection and edits

React when the user picks an item (or commits a typed value):

combo.SelectedItemChanged += (s, e) =>
{
    Console.WriteLine($"Selected: {combo.SelectedItem}");
};

Capture new values the user typed and keep them for later suggestions (when the cell is backed by your own list):

var items = new List<string> { "Alpha", "Beta" };
var combo = new ComboListCell(items);
sheet["B5"] = combo;

sheet.AfterCellEdit += (s, e) =>
{
    if (ReferenceEquals(e.Cell.Body, combo) &&
        e.NewData is string text &&
        !string.IsNullOrWhiteSpace(text) &&
        !items.Contains(text))
    {
        items.Add(text);
    }
};

Keyboard behavior matches common combo boxes: Up/Down moves through the list, Enter/Space confirms the highlighted item, Tab confirms and moves to the next cell, and Esc closes the drop-down.

Styling (WPF)

On WPF, adjust the list appearance through Style:

#if WPF
combo.Style.TextColor = SolidColor.DarkBlue;
combo.Style.BackColor = SolidColor.LightYellow;
combo.Style.FontSize = 14;
combo.Style.FontWeight = FontWeights.Bold;
#endif

Override the ListBox template (WPF)

You can swap in a custom ControlTemplate/ItemTemplate for the drop-down ListBox. Define the templates in XAML and assign them when the drop-down opens:

<Window.Resources>
  <ControlTemplate x:Key="ReoGridComboListTemplate" TargetType="ListBox">
    <Border Background="#101820" CornerRadius="6" Padding="4">
      <ScrollViewer Focusable="False">
        <ItemsPresenter />
      </ScrollViewer>
    </Border>
  </ControlTemplate>

  <DataTemplate x:Key="ReoGridComboItemTemplate">
    <StackPanel Orientation="Horizontal" Margin="4,2">
      <Ellipse Width="6" Height="6" Fill="#FF7A00" Margin="0,0,6,0"/>
      <TextBlock Text="{Binding}" Foreground="White"/>
    </StackPanel>
  </DataTemplate>
</Window.Resources>

Wire it up in code:

#if WPF
combo.DropdownOpened += (s, e) =>
{
    if (((ComboListCell)s).DropdownControl is ListBox listBox)
    {
        listBox.Template = (ControlTemplate)FindResource("ReoGridComboListTemplate");
        listBox.ItemTemplate = (DataTemplate)FindResource("ReoGridComboItemTemplate");
    }
};
#endif

Extend the control

Subclass ComboListCell when you need deeper customization (e.g., overriding keyboard handling or providing specialized data binding):

class MyComboListCell : ComboListCell
{
    // override members or add helpers here
}