WPF：列表框内的情节提要触发器

Question

I have a ListBox where it's DataTemplate is as follows:

<DataTemplate>
    <Grid >
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="120"/>
            <ColumnDefinition Width="180"/>
            <ColumnDefinition />
            <ColumnDefinition Width="180"/>
            <ColumnDefinition Width="180" />
        </Grid.ColumnDefinitions>

        <ComboBox Name="modes" ItemsSource="{Binding Modes}" Margin="10,3"/>

        <ComboBox Name="companyName" ItemsSource="{Binding Companies}" Grid.Column="1" IsEditable="True" Width="0" Margin="10,3">
            <ComboBox.Style>
                <Style TargetType="ComboBox">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding Path=SelectedIndex, ElementName=modes}" Value="0" >
                            <DataTrigger.EnterActions>
                                <BeginStoryboard >
                                    <Storyboard >
                                        <DoubleAnimation Storyboard.TargetProperty="Width"
                                 From="0" To="170" Duration="200"/>
                                    </Storyboard>
                                </BeginStoryboard>
                            </DataTrigger.EnterActions>
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </ComboBox.Style>
        </ComboBox>

        <TextBox Grid.Column="2" Margin="3"/>
        <TextBox Grid.Column="3" Margin="3"/>

        <ComboBox ItemsSource="{Binding Providers}" Grid.Column="4" IsEditable="True" Margin="10,3"/>
    </Grid>
</DataTemplate>

What I want to do is that when I choose the first item in modes , companyName 's Width would expand to 170, but nothing happens when I try this.

Can anyone tell me where is the error in my code?

Answer 1

Your duration attribute is not specific.

What is 200?

WPF Animation Duration