Create drop-down list cell

To create drop-down list cell, use DropDownListCell class, which is a built-in cell body to represent drop-down list in specified cell.

var sheet = grid.CurrentWorksheet;

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

sheet["B2"] = dropdown;

Result:

Change list items

Use Items property to add, remove and clear the list items:

dropdown.Items.AddRange("Apple", "Orange", "Banana", "Pear", "Pumpkin", "Cherry", "Coconut");

Set default data

To set a default data or change the cell data, directly set the data of cell:

sheet["B2"] = "Apple";

Result:

Get selected data

Use either following method to get event when user selected an item.

• Event SelectedItemChanged of instance of DropDownListCell
• Event CellDataChanged of instance of Worksheet

To use SelectedItemChanged event, use the following code:

dropdown.SelectedItemChanged += (s,e) => { ... };

Since drop-down list cell will update the data of cell after item is selected by user, it is also possible to use the CellDataChanged event to get selected data:

sheet.CellDataChanged += (s, e) => {
  if (e.Cell.Position == new CellPosition("E5")) {
    MessageBox.Show("Drop-down list item selected: " + e.Cell.Data);
  }
};

Change drop-down cell size

There are many methods to change a drop-down cell width, according to the layout of worksheet, use one of following method to change size:

1. Change size of header (row or column that includes the cell)
2. Merge drop-down cell with neighbor cells
3. Give cell a Padding style

Change header size

Set the header size by using SetColumnsWidth and SetRowsHeight method will also change the cell's size:

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

Result:

Change row height:

sheet.RowHeaders[1].Height = 40;

Result:

Merge cells

By merging two neighbor cells to make larger size:

sheet.MergeRange("B2:C2");

Result:

Set padding style

Set a padding style for cell to shrink the drop-down control size inside cell:

// Set right padding 10px
sheet.Cells["B2"].Style.Padding = new Padding(0, 0, 10, 0);

Change drop-down button size

The following two properties are related to change button size:

• DropdownButtonAutoHeight
• DropdownButtonSize

DropdownButtonAutoHeight property indicates that fit the drop-down button to the cell automatically, by default this property is true; DropdownButtonSize property used to set the drop-down button size directly. When DropdownButtonAutoHeight is true, the height of drop-down button size will not function.

Auto-height is true:

Auto-height is false:

When DropdownButtonAutoHeight is false, changing the DropdownButtonSize property to adjust the button size:

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

Set cell border

A drop-down cell doesn't show borders around itself, instead set the cell border styles to show borders:

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

Draw custom drop-down button

By overriding method OnPaintDropdownButton to draw custome drop-down button:

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 custom drop-down cell

It is possible to make custom drop-down cell to put any Windows form controls into the drop-down panel.

See how to create custom drop-down cell.