如何在绑定WPF中使用if表达式-C＃

Question

Here is my code:

<ListView Grid.Row="1" x:Name="viewTicket" Style="{StaticResource ticketListBox}" ScrollViewer.HorizontalScrollBarVisibility="Disabled" Background="Transparent" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Center" BorderBrush="{x:Null}" SelectionChanged="ViewTicket_SelectionChanged">
    <ListView.ItemTemplate>
        <DataTemplate>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="*"/>
                    <RowDefinition Height="*"/>
                </Grid.RowDefinitions>
                <Grid Grid.Row="0">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="4*"/>
                        <ColumnDefinition Width="2*"/>
                    </Grid.ColumnDefinitions>
                    <Image Visibility="{Binding selectedCheck}" Name="check" Grid.Column="0" Margin="10,0,0,0" HorizontalAlignment="Left" VerticalAlignment="Center" Source="../../Images/check-donatota.png" Stretch="None" MouseLeftButtonUp="Check_MouseLeftButtonUp"/>
                    <TextBlock Visibility="{Binding selectedQuantity}" Name="quantity" Grid.Column="0" HorizontalAlignment="Center" VerticalAlignment="Center" TextWrapping="Wrap" Text="{Binding amount}"/>
                    <TextBlock Grid.Column="1" HorizontalAlignment="Left" VerticalAlignment="Center" Foreground="Black" TextWrapping="Wrap" Text="{Binding name}"/>
                    <TextBlock Visibility="{Binding selectedPrice}" Name="price" Grid.Column="2" HorizontalAlignment="Right" VerticalAlignment="Center" TextWrapping="Wrap" Text="{Binding total, StringFormat=C}"/>
                    <Image Visibility="{Binding selectedTrash}" Name="trash" Grid.Column="2" Margin="0,0,15,0" HorizontalAlignment="Right" VerticalAlignment="Center" Source="../../Images/trash-donatota.png" Stretch="None" MouseLeftButtonUp="Trash_MouseLeftButtonUp"/>
                </Grid>

                <ListView 
                    ItemsSource="{Binding ingredients}" 
                    Grid.Row="1" 
                    Margin="-5,0,0,0" 
                    Name="viewTicketIngs" 
                    IsHitTestVisible="False" 
                    Style="{StaticResource ticketListBox}"
                    ScrollViewer.HorizontalScrollBarVisibility="Disabled" 
                    ScrollViewer.VerticalScrollBarVisibility="Hidden" 
                    Background="Transparent" 
                    HorizontalContentAlignment="Stretch" 
                    VerticalContentAlignment="Center" 
                    BorderBrush="{x:Null}" 
                    SelectionChanged="ViewTicketIngs_SelectionChanged">
                    <ListView.ItemTemplate>
                        <DataTemplate>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="*"/>
                                    <ColumnDefinition Width="4*"/>
                                    <ColumnDefinition Width="2*"/>
                                </Grid.ColumnDefinitions>
                                <TextBlock Visibility="Visible" Name="quantity" Grid.Column="0" Foreground="{DynamicResource GrayTextDonaTotaBrush}" HorizontalAlignment="Center" VerticalAlignment="Center" TextWrapping="Wrap" Text="{Binding amount}"/>
                                <TextBlock Margin="10,0,0,0" Grid.Column="1" Foreground="{DynamicResource GrayTextDonaTotaBrush}" HorizontalAlignment="Left" VerticalAlignment="Center" TextWrapping="Wrap" Text="{Binding ing.name}"/>
                                <TextBlock Visibility="Visible" Name="price" Grid.Column="2" Foreground="{DynamicResource GrayTextDonaTotaBrush}" HorizontalAlignment="Right" VerticalAlignment="Center" TextWrapping="Wrap" Text="{Binding total, StringFormat=C}"/>
                            </Grid>
                        </DataTemplate>
                    </ListView.ItemTemplate>
                </ListView>
            </Grid>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

I add data to the ListView viewTicket , but depending of a property I would like to change the ItemSource Binding of the ListView viewTicketIngs . In other words, is there anyway that I can use an if expression on the binding? Something like ItemsSource="{Binding IF(mode == 0) {ingredients} else {plates}}"

Answer 1

Change the Binding by a DataTrigger in a Style:

<ListView ...>
    <ListView.Style>
        <Style TargetType="ListView">
            <Setter Property="ItemsSource" Value="{Binding plates}"/>
            <Style.Triggers>
                <DataTrigger Binding="{Binding mode}" Value="0">
                    <Setter Property="ItemsSource" Value="{Binding ingredients}"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </ListView.Style>
</ListView>

Answer 2

As I understand it, you sometimes dispaly plates, sometimes ingredients. Now there are triggers conditional display. WPF actually has a pretty wide support.

However what might be better is to have 2 different ViewModel classes and two (how I call them) "type targetting data tempaltes". Say you have these clases:

abstract class ViewModelItem { }

class Plate : ViewModelItem { }

class IngredientsList : ViewModelItem { }

The propety you exposie this in, would be set to ViewModelItem . In realtiy you would assign either a Plate or IngredientsList Instance.

Now you define two DataTemplates. A interesting thing about WPF is that if you do not specify a explicit Template, the Code will go out of it's way to try to find one. And it will do the matching via the DataType property of the Template (TargetType for Styles and similar). It works similar to what CSS does, with somebodies code going out of it's way to find a template to apply.