How to change the dropdown height in WinForms GridGroupingControl?

this.gridGroupingControl1.QueryCellStyleInfo += new GridTableCellStyleInfoEventHandler(gridGroupingControl1_QueryCellStyleInfo);
this.gridGroupingControl1.TableControlCurrentCellShowingDropDown += new GridTableControlCurrentCellShowingDropDownEventHandler(gridGroupingControl1_TableControlCurrentCellShowingDropDown);

void gridGroupingControl1_TableControlCurrentCellShowingDropDown(object sender, GridTableControlCurrentCellShowingDropDownEventArgs e)
{
   if(this.gridGroupingControl1.TableModel.CurrentCellRenderer != null && this.gridGroupingControl1.TableModel.CurrentCellRenderer is GridDropDownGridListControlCellRenderer)
   {
      int defaultHeight=18;
      GridDropDownGridListControlCellRenderer listRenderer = (GridDropDownGridListControlCellRenderer)this.gridGroupingControl1.TableModel.CurrentCellRenderer;
      if(isitem1)
      {
         e.Inner.Size = new Size(100, (items1.Count * defaultHeight));//Set the height based on the items.
      }
      else if(isitem2)
      {
         e.Inner.Size = new Size(100, (items2.Count * defaultHeight));//Set the height based on the items.
      }
      listRenderer.ListControlPart.ShowColumnHeader = false;
   }
}

void gridGroupingControl1_QueryCellStyleInfo(object sender, GridTableCellStyleInfoEventArgs e)
{
   double result = 0;
   if(e.TableCellIdentity.Column != null)
   {
      if(e.TableCellIdentity.Column.GetName().Equals("PaymentType") && e.TableCellIdentity.DisplayElement.GetRecord() != null)
      {
         If (double.TryParse(e.TableCellIdentity.DisplayElement.GetRecord().GetValue("Amount").ToString(), out result))
         {
            //Bind the DataSource for drop down combo box cell based on the ‘Amount’ column.
            if(result > 0)
            {
               e.Style.DataSource = items1;
               isitem2 = false;
               isitem1 = true;
            }
            else
            {
               e.Style.DataSource = items2;
               isitem2 = true;
               isitem1 = false;
            }
         }
         e.Style.CellType = GridCellTypeName.GridListControl;//To set Combobox Celltype.
         e.Style.ShowButtons = GridShowButtons.Show;
         e.Style.DropDownStyle = GridDropDownStyle.Editable;//This allows you to edit the combo box contents.
         e.Style.AutoCompleteInEditMode = GridComboSelectionOptions.AutoSuggest;//Auto complete support for combobox in edit mode.
      }
   }
}

AddHandler gridGroupingControl1.QueryCellStyleInfo, AddressOf gridGroupingControl1_QueryCellStyleInfo
AddHandler gridGroupingControl1.TableControlCurrentCellShowingDropDown, AddressOf gridGroupingControl1_TableControlCurrentCellShowingDropDown

Private Sub gridGroupingControl1_TableControlCurrentCellShowingDropDown(ByVal sender As Object, ByVal e As GridTableControlCurrentCellShowingDropDownEventArgs)
   If Me.gridGroupingControl1.TableModel.CurrentCellRenderer IsNot Nothing AndAlso TypeOf Me.gridGroupingControl1.TableModel.CurrentCellRenderer Is GridDropDownGridListControlCellRenderer Then
      Dim defaultHeight As Integer=18
      Dim listRenderer As GridDropDownGridListControlCellRenderer = CType(Me.gridGroupingControl1.TableModel.CurrentCellRenderer, GridDropDownGridListControlCellRenderer)
      If isitem1 Then
         e.Inner.Size = New Size(100, (items1.Count * defaultHeight)) ‘Set the height based on the items.
      ElseIf isitem2 Then
         e.Inner.Size = New Size(100, (items2.Count * defaultHeight)) ‘Set the height based on the items.
      End If
      listRenderer.ListControlPart.ShowColumnHeader = False
   End If
End Sub

Private Sub gridGroupingControl1_QueryCellStyleInfo(ByVal sender As Object, ByVal e As GridTableCellStyleInfoEventArgs)
   Dim result As Double = 0
   If e.TableCellIdentity.Column IsNot Nothing Then
      If e.TableCellIdentity.Column.GetName().Equals("PaymentType") AndAlso e.TableCellIdentity.DisplayElement.GetRecord() IsNot Nothing Then
         If Double.TryParse(e.TableCellIdentity.DisplayElement.GetRecord().GetValue("Amount").ToString(), result) Then
            ‘Bind the DataSource for drop down combo box cell based on the ‘Amount’ column.
            If result > 0 Then
               e.Style.DataSource = items1
               isitem2 = False
               isitem1 = True
            Else
               e.Style.DataSource = items2
               isitem2 = True
               isitem1 = False
            End If
         End If
         e.Style.CellType = GridCellTypeName.GridListControl 'To set Combobox Celltype.
         e.Style.ShowButtons = GridShowButtons.Show
         e.Style.DropDownStyle = GridDropDownStyle.Editable 'This allows the user to edit the combo box contents.
         e.Style.AutoCompleteInEditMode = GridComboSelectionOptions.AutoSuggest 'Auto complete support for combobox in edit mode.
      End If
   End If
End Sub