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How to control the number of visible items in a ComboBox cell in WinForms GridControl?

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Show the dropdown of combobox in a cell

In order to control the items showing in dropdown of combo box, GridComboBoxListBoxPart.DropDownRows property can be used. The GridComboBoxListBoxPart is the actual control type of the list that is dropped to display the items. But it is buried a little deep and generally needs an event handler to set it in WinForms GridControl.

The reason for using an event handler is that normally a single ComboBox control is shared among all ComboBox cells. Each cell can potentially have a different list and may need different numbers of visible rows. So, to handle this, you must catch Grid.CurrentCellShowingDropDown event and set the property there depending upon the exact row and column.


gridControl1.CurrentCellShowingDropDown += gridControl1_CurrentCellShowingDropDown;
void gridControl1_CurrentCellShowingDropDown(object sender, GridCurrentCellShowingDropDownEventArgs e)
   GridControlBase grid = sender as GridControlBase;
   if (grid != null)
      GridCurrentCell cc = grid.CurrentCell;
      GridComboBoxCellRenderer cr = cc.Renderer as GridComboBoxCellRenderer;
      //Sets number of visible items for comboboxes in Row 6 as 4, Row 4 as 7, Row 2 as 10 , and so on. 
      if (cc != null)
         if (cc.RowIndex == 6)
            ((GridComboBoxListBoxPart)cr.ListBoxPart).DropDownRows = 4;
         else if (cc.RowIndex == 4)
            ((GridComboBoxListBoxPart)cr.ListBoxPart).DropDownRows = 7;
         else if (cc.RowIndex == 2)
            ((GridComboBoxListBoxPart)cr.ListBoxPart).DropDownRows = 10;
         else ((GridComboBoxListBoxPart)cr.ListBoxPart).DropDownRows = 6;



Private gridControl1.CurrentCellShowingDropDown += AddressOf gridControl1_CurrentCellShowingDropDown
Private Sub gridControl1_CurrentCellShowingDropDown(ByVal sender As Object, ByVal e As GridCurrentCellShowingDropDownEventArgs)
   Dim grid As GridControlBase = TryCast(sender, GridControlBase)
   If grid IsNot Nothing Then
 Dim cc As GridCurrentCell = grid.CurrentCell
 Dim cr As GridComboBoxCellRenderer = TryCast(cc.Renderer, GridComboBoxCellRenderer)
   'Sets number of visible items for comboboxes in Row 6 as 4, Row 4 as 7, Row 2 as 10 , and so on. 
   If cc IsNot Nothing Then
      If cc.RowIndex = 6 Then
 CType(cr.ListBoxPart, GridComboBoxListBoxPart).DropDownRows = 4
      ElseIf cc.RowIndex = 4 Then
 CType(cr.ListBoxPart, GridComboBoxListBoxPart).DropDownRows = 7
      ElseIf cc.RowIndex = 2 Then
 CType(cr.ListBoxPart, GridComboBoxListBoxPart).DropDownRows = 10
  CType(cr.ListBoxPart, GridComboBoxListBoxPart).DropDownRows = 6
      End If
   End If
 End If
End Sub



Dropdown of combobox in a cell


C#: DropDownRows_ComboBox_CS

VB: DropDownRows_ComboBox_VB



I hope you enjoyed learning about how to control the number of visible items in a ComboBox cell in WinForms GridControl.

You can refer to our  WinForms GridControl feature tour page to know about its other groundbreaking feature representations. You can also explore our WinForms GridControl documentation to understand how to create and manipulate data.

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