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DropDown Resizing

RadDropDownList supports different sizing modes, based on the DropDownSizingMode property of the control.

The SizingMode enumeration has the following members:

  • None: no sizing is allowed.

Figure 1: SizingMode.None

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this.radDropDownList1.DropDownSizingMode = SizingMode.None;

Me.radDropDownList1.DropDownSizingMode = SizingMode.None

  • RightBottom: allows sizing in horizontal direction.

Figure 2: SizingMode.RightBottom

dropdown-and-listcontrol-dropdownlist-dropdown-resizing 002


this.radDropDownList1.DropDownSizingMode = SizingMode.RightBottom;

Me.radDropDownList1.DropDownSizingMode = SizingMode.RightBottom

  • UpDown: allows sizing in vertical direction.

Figure 3: SizingMode.UpDown

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this.radDropDownList1.DropDownSizingMode = SizingMode.UpDown;

Me.radDropDownList1.DropDownSizingMode = SizingMode.UpDown

  • UpDownAndRightBottom: allows sizing in both directions.

Figure 4: SizingMode.UpDownAndRightBottom

dropdown-and-listcontrol-dropdownlist-dropdown-resizing 004


this.radDropDownList1.DropDownSizingMode = SizingMode.UpDownAndRightBottom;

Me.radDropDownList1.DropDownSizingMode = SizingMode.UpDownAndRightBottom

Fixed size

You can specify a fixed height or width of the drop-down by setting the DropDownHeight and DropDownWidth properties.

Figure 5: DropDownHeight

dropdown-and-listcontrol-dropdownlist-dropdown-resizing 005


this.radDropDownList1.DropDownListElement.DropDownHeight = 400;

Me.radDropDownList1.DropDownListElement.DropDownHeight = 400

Figure 6: DropDownWidth

dropdown-and-listcontrol-dropdownlist-dropdown-resizing 007


this.radDropDownList1.DropDownListElement.DropDownWidth = 400;

Me.radDropDownList1.DropDownListElement.DropDownWidth = 400

You can set the DropDownMinSize property in order to specify the exact minimum height and width for the drop-down.

Figure 7: DropDownMinSize

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this.radDropDownList1.DropDownMinSize = new Size(400, 400);

Me.radDropDownList1.DropDownMinSize = New Size(400, 400)

Auto size

The following example demonstrates a sample approach how to handle the RadDropDownList.PopupOpening event and achieve auto size functionality for the pop up in RadDropDownList:

Auto size drop down

private void RadDropDownList1_PopupOpening(object sender, CancelEventArgs e)
    RadDropDownListElement list = sender as RadDropDownListElement;
    float width = 0;
    for (int x = 0; x < list.Items.Count(); x++)
        width = Math.Max(width, TextRenderer.MeasureText(list.Items[x].Text, list.Font).Width);
    if (list.Items.Count * (list.ItemHeight-1) > list.DropDownHeight)
        width += list.ListElement.VScrollBar.Size.Width;
    list.Popup.Width = (int)width;

Private Sub RadDropDownList1_PopupOpening(sender As Object, e As CancelEventArgs)
    Dim list As RadDropDownListElement = TryCast(sender, RadDropDownListElement)
    Dim width As Single = 0
    For x As Integer = 0 To list.Items.Count() - 1
        width = Math.Max(width, TextRenderer.MeasureText(list.Items(x).Text, list.Font).Width)
    If list.Items.Count * (list.ItemHeight - 1) > list.DropDownHeight Then
        width += list.ListElement.VScrollBar.Size.Width
    End If
    list.Popup.Width = CInt(width)
End Sub
'#End Region
'#Region "FilteringPredicate"
Private Function FilterItem(item As RadListDataItem) As Boolean
    If item.Text.StartsWith("L") Then
        Return True
    End If

    Return False
End Function

Default pop up size Auto sized popup
dropdown-and-listcontrol-dropdownlist-dropdown-resizing 009 dropdown-and-listcontrol-dropdownlist-dropdown-resizing 010

Displayed items

By default, RadDropDownList displays 6 items in the pop-up. In case you need to change this number you can set the DefaultItemsCountInDropDown property:

Figure 8: DefaultItemsCountInDropDown

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this.radDropDownList1.DropDownListElement.DefaultItemsCountInDropDown = 3;

Me.radDropDownList1.DropDownListElement.DefaultItemsCountInDropDown = 3

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