How to change the dropdown window height of a combobox that is used in a grid control cell

[Dongxian Li]

I am using ComboBox cell type in my virtual grid. My question is:
Is there a way to set the ComboBox dropdown window height to a larger number when the choicelist is long? For example, if the ComboBox has 10 items, I would like the ComboBox dropdown window expanded to show all 10 items instead of only showing 6 of them with a scrollbar.

Thanks
dongxian

[Administrator]

You set the DropDownRows property. This can be done one time in formload if you want all comboboxes to have the same number of rows. But if you need to do it on a cell by cell basis, you can use the CurrentCellShowingDropDown event.

private 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;
		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;
		}
	}
}

[Dongxian Li]

I tried your code. It works fine except for a small problem. The dropdown window looks fine when the DropDownRows is less than 8.
But when the DropDownRows reaches 8, a extra empty row was added to the dropdown window.
When the DropDownRows reaches 16, two extra empty rows were added to the dropdown window.
When the DropDownRows reaches 24, three extra empty rows were added to the dropdown window.

Looks like one extra empty row is added to the dropdown window every 8 rows.

thanks

[Administrator]

This appears to be a bug. We will get it fixed in our code.

[Tommy Heath]

How IS it done in Formload? And how do you set the dropDownRows and or the drop down height for a non-grid comboBoxBase with/without a grid ListControlPart?

>You set the DropDownRows property. This can be done one time in formload if you want all comboboxes to have the same number of rows. But if you need to do it on a cell by cell basis, you can use the CurrentCellShowingDropDown event.
>

>private 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;
>		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;
>		}
>	}
>}
>

[Administrator]

The reason you normally do it in CurrentCellShowing dropdown is that the same combobox is used for every cell.If you set it in FormLoad, then it will be set for every cell.

private void Form1_Load(object sender, System.EventArgs e)
{
	GridComboBoxCellRenderer cr = this.gridControl1.GetCellRenderer(5, 3) as GridComboBoxCellRenderer;
	((GridComboBoxListBoxPart)cr.ListBoxPart).DropDownRows = 2;
}

I think for the comboboxbase, the height of the dropdown is determined by the height of teh ListControl that you are using for your dropdown list.

[Karsten Brocksieper]

Hello,

I can´t read C# code very well. Therefore it would be very nice if someone can translate the above mentioned code for VB.Net.

Thank you very much in advance

Karsten

>The reason you normally do it in CurrentCellShowing dropdown is that the same combobox is used for every cell.If you set it in FormLoad, then it will be set for every cell.
>

>private void Form1_Load(object sender, System.EventArgs e)
>{
>	GridComboBoxCellRenderer cr = this.gridControl1.GetCellRenderer(5, 3) as GridComboBoxCellRenderer;
>	((GridComboBoxListBoxPart)cr.ListBoxPart).DropDownRows = 2;
>}
>

>
>I think for the comboboxbase, the height of the dropdown is determined by the height of teh ListControl that you are using for your dropdown list.

[Administrator]

Hi Karsten,

Here is the VB code snippet.

'' Form load event
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Dim cr As GridComboBoxCellRenderer = Me.gridControl1.GetCellRenderer(5,3)
CType(cr.ListBoxPart, GridComboBoxListBoxPart).DropDownRows = 2
End Sub

'' In CurrentCellShowingDropDown event
Private Sub gridControl1_CurrentCellShowingDropDown(ByVal sender As Object, ByVal e As Syncfusion.Windows.Forms.Grid.GridCurrentCellShowingDropDownEventArgs) Handles gridControl1.CurrentCellShowingDropDown
Dim cc As GridCurrentCell = Me.gridControl1.GetCellRenderer(5,3).CurrentCell
Dim cr As GridComboBoxCellRenderer = Me.gridControl1.GetCellRenderer(5,3)
CType(cr.ListBoxPart, GridComboBoxListBoxPart).DropDownRows = 10
End Sub ''gridControl1_CurrentCellShowingDropDown

Let us know if you need further assistance,

Best Regards,
Madhan.