WPF：绑定到网格的“Horizo​​ntalAlignment”属性

Question

I am writing a chatclient and my messages get displayed in a listbox. In the xaml my listbox is set up like this:

<ListBox x:Name="list_chat" Background="{x:Null}" VerticalContentAlignment="Stretch" HorizontalContentAlignment="Stretch" Margin="256,0,0,64" BorderThickness="0" BorderBrush="{x:Null}" Foreground="White" ScrollViewer.HorizontalScrollBarVisibility="Disabled" ScrollViewer.VerticalScrollBarVisibility="Visible" ScrollViewer.CanContentScroll="False" Focusable="False" Grid.ColumnSpan="2">
                        <ListBox.ItemTemplate>
                            <DataTemplate>
                                <Grid Background="#bd93f9" Margin="64,0,8,0" HorizontalAlignment="Right">
                                    <TextBlock Text="{Binding}" TextWrapping="Wrap" LineStackingStrategy="MaxHeight" Foreground="White" HorizontalAlignment="Right" VerticalAlignment="Stretch" Margin="16,8,32,0" LineHeight="Auto" TextTrimming="None" TextAlignment="Right" Width="Auto" Padding="0" UseLayoutRounding="True">
                                    </TextBlock>
                                    <Button HorizontalAlignment="Right" VerticalAlignment="Center" Width="32" Height="32" Background="{x:Null}" BorderBrush="{x:Null}" Foreground="White" Margin="0">
                                        <Button.Style>
                                            <Style TargetType="{x:Type Button}">
                                                <Setter Property="Template">
                                                    <Setter.Value>
                                                        <ControlTemplate TargetType="Button">
                                                            <Border
                                    x:Name="border"
                                    Background="{x:Null}"
                                    BorderBrush="{x:Null}"
                                    BorderThickness="0"
                                    CornerRadius="90"
                                    TextBlock.Foreground="White">
                                                                <Grid>
                                                                    <Image
                                            x:Name="buttonImage"
                                            Source="C:\Users\janke\source\repos\Unichat\Unichat\bin\Debug\pictures\icons\reply-line.png" Width="16" Height="16"
                                            />
                                                                    <ContentPresenter
                                            Margin="{TemplateBinding Padding}"
                                            HorizontalAlignment="Center"
                                            VerticalAlignment="Center" />
                                                                </Grid>
                                                            </Border>
                                                            <ControlTemplate.Triggers>
                                                                <Trigger Property="IsMouseOver" Value="true">
                                                                    <Setter TargetName="border" Property="Background" Value="{x:Null}" />
                                                                    <Setter TargetName="border" Property="BorderBrush" Value="{x:Null}" />
                                                                    <Setter TargetName="buttonImage" Property="Source" Value="C:\Users\janke\source\repos\Unichat\Unichat\bin\Debug\pictures\icons\reply-fill.png" />
                                                                </Trigger>
                                                                <Trigger Property="IsPressed" Value="true">
                                                                    <Setter TargetName="border" Property="Background" Value="{x:Null}" />
                                                                    <Setter TargetName="border" Property="BorderBrush" Value="{x:Null}" />
                                                                </Trigger>
                                                            </ControlTemplate.Triggers>
                                                        </ControlTemplate>
                                                    </Setter.Value>
                                                </Setter>
                                            </Style>
                                        </Button.Style>
                                    </Button>
                                </Grid>
                            </DataTemplate>
                        </ListBox.ItemTemplate>
                    </ListBox>

I want to control the "HorizontalAlignment" of my grid property with a binding so the message either gets aligned right or left, depending on if the message is sent or recieved. I didn't find a way to do that on the internet, even though I know its possible. I just don't understand bindings just yet.

My C# code looks like this:

list_chat.Items.Add(textRange.Text);

Thanks in advance!

Answer 1

The HorizontalAlignment property takes a type of System.Windows.HorizontalAlignment. You want to bind to a property of that type.

public HorizontalAlignment HorizontalAlignmentValue 
{
   get
   {
      if (--whatever--)
          return HorizontalAlignment.Left;
      else if (--whatever--)
          return HorizontalAlignment.Right;
   }
}

Then you would just set up the binding like usual. If you will need to update this value then be sure to implement INotifyPropertyChanged.

For the binding (in it simplest form):

<Grid HorizontalAlignment="{Binding HorizontalAlignmentValue}" />

Alt:

If you don't want the 'HorizontalAlignmentValue' property to handle its own logic, then you could set up the property with INotifyPropertyChanged and set it elsewhere presumably where the value can be determined, then control updating the UI on change.