How to differentiate combobox column from other columns in non-editable display mode in WinForms DataGrid (SfDataGrid)

Differentiate combobox column from other columns

Normally, the drop-down arrow for GridComboBoxColumn will be shown only in the edit mode. You can differentiate the combo box column from other columns by showing the drop-down arrow in the display mode by creating custom renderer for the combo box column.

C#

public Form1()
{
    InitializeComponent();
    this.sfDataGrid1.CellRenderers["ComboBox"] = new CustomComboBoxCellRenderer();
}
 
public class CustomComboBoxCellRenderer : GridComboBoxCellRenderer
{
    protected override void OnRender(Graphics paint, Rectangle cellRect, string cellValue, CellStyleInfo style, DataColumnBase column, Syncfusion.WinForms.GridCommon.ScrollAxis.RowColumnIndex rowColumnIndex)
    {
        base.OnRender(paint, cellRect, cellValue, style, column, rowColumnIndex);
        var dropDownbuttonRect = new Rectangle(cellRect.X + cellRect.Width - 17, cellRect.Y + (cellRect.Height / 2), 8, 4);
        paint.DrawLine(new Pen(Color.Gray), dropDownbuttonRect.X, dropDownbuttonRect.Y, dropDownbuttonRect.X + (dropDownbuttonRect.Width / 2), dropDownbuttonRect.Y + dropDownbuttonRect.Height);
        paint.DrawLine(new Pen(Color.Gray), dropDownbuttonRect.X + dropDownbuttonRect.Width, dropDownbuttonRect.Y, dropDownbuttonRect.X + (dropDownbuttonRect.Width / 2), dropDownbuttonRect.Y + dropDownbuttonRect.Height);
    }
}

VB

Public Sub New()
    InitializeComponent()
    Me.sfDataGrid1.CellRenderers("ComboBox") = New CustomComboBoxCellRenderer()
End Sub
 
Public Class CustomComboBoxCellRenderer
    Inherits GridComboBoxCellRenderer
    Protected Overrides Sub OnRender(ByVal paint As Graphics, ByVal cellRect As Rectangle, ByVal cellValue As String, ByVal style As CellStyleInfo, ByVal column As DataColumnBase, ByVal rowColumnIndex As Syncfusion.WinForms.GridCommon.ScrollAxis.RowColumnIndex)
        MyBase.OnRender(paint, cellRect, cellValue, style, column, rowColumnIndex)
        Dim dropDownbuttonRect = New Rectangle(cellRect.X + cellRect.Width - 17, cellRect.Y + (cellRect.Height \ 2), 8, 4)
        paint.DrawLine(New Pen(Color.Gray), dropDownbuttonRect.X, dropDownbuttonRect.Y, dropDownbuttonRect.X + (dropDownbuttonRect.Width \ 2), dropDownbuttonRect.Y + dropDownbuttonRect.Height)
        paint.DrawLine(New Pen(Color.Gray), dropDownbuttonRect.X + dropDownbuttonRect.Width, dropDownbuttonRect.Y, dropDownbuttonRect.X + (dropDownbuttonRect.Width \ 2), dropDownbuttonRect.Y + dropDownbuttonRect.Height)
    End Sub
End Class