The DropdownListCell is a built-in cell body that displays a drop-down list for single item selection. It extends DropdownCell, inheriting the drop-down panel infrastructure.

Namespace

using unvell.ReoGrid.CellTypes;

Create a Drop-down List Cell

var sheet = grid.CurrentWorksheet;

var dropdown = new DropdownListCell(
    "Apple", "Orange", "Banana", "Pear",
    "Pumpkin", "Cherry", "Coconut"
);

sheet["B2"] = dropdown;

Result:

Constructors

Using a Cell Range as Data Source

You can bind the drop-down list to a range of cells so the items update automatically:

// Items come from cells A1:A10
var dropdown = new DropdownListCell(sheet.Ranges["A1:A10"]);
sheet["C1"] = dropdown;

Using a Mutable List

Pass a List<string> to keep the items in sync:

var items = new List<string> { "Alpha", "Beta", "Gamma" };
var dropdown = new DropdownListCell(items);
sheet["B2"] = dropdown;

// Add items later — they appear in the dropdown
items.Add("Delta");

Properties

DropdownListCell Properties

Inherited from DropdownCell

DropdownCellStyle Properties

Events

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

Since the drop-down list cell updates the cell data after an item is selected, the worksheet CellDataChanged event also fires:

sheet.CellDataChanged += (s, e) =>
{
    if (e.Cell.Position == new CellPosition("B2"))
    {
        Console.WriteLine("Selected: " + e.Cell.Data);
    }
};

Methods

// Open the dropdown programmatically
dropdown.PushDown();

// Close it
dropdown.PullUp();

Set Default Data

To set a default value or change the cell data:

sheet["B2"] = "Apple";

Result:

Change Drop-down Cell Size

Change Column Width

sheet.ColumnHeaders["B"].Width = 120;

Change Row Height

sheet.RowHeaders[1].Height = 40;

Merge Cells

sheet.MergeRange("B2:C2");

Set Padding Style

Shrink the drop-down control within the cell:

sheet.Cells["B2"].Style.Padding = new Padding(0, 0, 10, 0);

Change Drop-down Button Size

dropdown.DropdownButtonAutoHeight = false;
dropdown.DropdownButtonSize = new System.Drawing.Size(40, 15);

When DropdownButtonAutoHeight is true (default), the button stretches to fill the cell height. Set to false to use a fixed size:

Set Cell Border

A drop-down cell does not show borders by default. Add borders explicitly:

sheet.Ranges["B2"].BorderOutside = BorderStyle.GraySolid;

Open on Cell Click

By default, the dropdown opens only when the dropdown button is clicked. Set PullDownOnClick to open on any click within the cell:

dropdown.PullDownOnClick = true;

WPF Styling

On WPF, customize the list appearance through the Style property:

#if WPF
dropdown.Style.TextColor = SolidColor.DarkBlue;
dropdown.Style.BackColor = SolidColor.LightYellow;
dropdown.Style.FontSize = 14;
dropdown.Style.FontWeight = FontWeights.Bold;
dropdown.Style.HorizontalAlignment = HorizontalAlignment.Left;
dropdown.Style.Padding = new PaddingValue(4, 4, 4, 4);
#endif

DropdownListStyle Properties (WPF Only)

Draw a Custom Drop-down Button

Override OnPaintDropdownButton to customize the button appearance:

class MyDropdownListCell : DropdownListCell
{
    public MyDropdownListCell(params string[] items) : base(items) { }

    protected override void OnPaintDropdownButton(CellDrawingContext dc, Graphics.Rectangle buttonRect)
    {
        dc.Graphics.DrawAndFillRectangle(buttonRect, SolidColor.DeepSkyBlue, new SolidColor("#BEE7F1"));

        var centerPoint = new Graphics.Point(buttonRect.Left + buttonRect.Width / 2,
            buttonRect.Top + buttonRect.Height / 2);

        GraphicsToolkit.FillTriangle(dc.Graphics.PlatformGraphics, 9,
            centerPoint, GraphicsToolkit.TriangleDirection.Down,
            this.IsDropdown ? Pens.SkyBlue : Pens.DarkSlateBlue);
    }
}

Make a Custom Drop-down Cell

Create custom drop-down cells that place any control inside the panel by extending DropdownCell:

See How to Create a Custom Drop-down Cell.

Class Hierarchy

CellBody
  └─ DropdownCell (base — panel, button, open/close)
       └─ DropdownListBaseCell (candidate source)
            ├─ DropdownListCell (selection-only list)
            └─ ComboListCell (editable combo with auto-complete)

Related Topics

• Built-in Cell Types — All cell type overview
• Combo List Cell — Editable combo box variant
• Custom Cell — Creating custom cell bodies
• How to Create Custom Drop-down Cell — Custom drop-down tutorial