xceed IntegerUpdown的TabIndex无效

Question

我有来自Xceed工具包的4 IntegerUpDowns。问题是通过Tab按钮导航根本不起作用。我设置了TabIndex，TabStop属性，但没有效果。也许有人有这个问题？任何帮助将不胜感激！非常感谢！

这是一段代码：

<GroupBox Margin="20"
                  HorizontalAlignment="Center"
                  Header="groupbox header text">
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <StackPanel Grid.Row="0"
                            Margin="7"
                            Orientation="Horizontal">
                    <TextBlock VerticalAlignment="Center" Text="text1:" />
                    <xctk:IntegerUpDown Name="updown1"
                                        Width="50"
                                        Height="25"
                                        Margin="17,0,30,0"
                                        TabIndex="0"
                                        IsTabStop="True"
                                        VerticalAlignment="Center"
                                        Increment="1"
                                        PreviewKeyDown="NumericUpDown_OnPreviewKeyDown"
                                        ValueChanged="Updown1_OnValueChanged"
                                        Value="{Binding Property1,
                                                        Mode=TwoWay,
                                                        UpdateSourceTrigger=PropertyChanged}" />
                    <TextBlock VerticalAlignment="Center" Text="text2" />
                    <xctk:IntegerUpDown Name="updown2"
                                        Width="50"
                                        Height="25"
                                        Margin="43,0,0,0"
                                        VerticalAlignment="Center"
                                        Increment="2"
                                        TabIndex="2"
                                        IsTabStop="True"
                                        PreviewKeyDown="NumericUpDown_OnPreviewKeyDown"
                                        Value="{Binding Property2,
                                                        Mode=TwoWay,
                                                        UpdateSourceTrigger=PropertyChanged}" />
                </StackPanel>
                <StackPanel Grid.Row="1"
                            Margin="7,0,7,7"
                            Orientation="Horizontal">
                    <TextBlock VerticalAlignment="Center" Text="text3:" />
                    <xctk:IntegerUpDown Name="updown3"
                                        Width="50"
                                        Height="25"
                                        Margin="7,0,30,0"
                                        VerticalAlignment="Center"
                                        Increment="1"
                                        TabIndex="1"
                                        IsTabStop="True"
                                        PreviewKeyDown="NumericUpDown_OnPreviewKeyDown"
                                        ValueChanged="Updown3_OnValueChanged"
                                        Value="{Binding Proeprty3,
                                                        Mode=TwoWay,
                                                        UpdateSourceTrigger=PropertyChanged}" />
                    <TextBlock VerticalAlignment="Center" Text="text4:"/>
                    <xctk:IntegerUpDown Name="updown4"
                                        Width="50"
                                        Height="25"
                                        Margin="7,0,0,0"
                                        TabIndex="3"
                                        VerticalAlignment="Center"
                                        Increment="1"
                                        IsTabStop="True"
                                        PreviewKeyDown="NumericUpDown_OnPreviewKeyDown"
                                        Value="{Binding Property4,
                                                        Mode=TwoWay,
                                                        UpdateSourceTrigger=PropertyChanged}" />
                </StackPanel>
            </Grid>
        </GroupBox>