带有字典的listbox，在初始页面加载时为selectedItem

Question

I have a dictionary which takes a string and a double, and I'm trying to get a selected element of the dictionary to be automatically selected (and highlighted) when I open the page that contains the listbox. I can get this working with a list of strings, but can't get it working with the dictionary.

<UserControl.Resources>
    <Style x:Key="MyLbStyle"
           TargetType="{x:Type ListBox}">
        <Style.Resources>
            <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}"
                             Color="Yellow" />
            <SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightBrushKey }"
                             Color="Yellow" />
            <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}"
                             Color="Black" />
            <SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightTextBrushKey}"
                             Color="Black" />
        </Style.Resources>
    </Style>
</UserControl.Resources>
<DockPanel Height="Auto"
           Width="Auto">
    <ListBox ItemsSource="{Binding MyDict, Mode=OneWay}"
             Style="{ StaticResource MyLbStyle}"
             DockPanel.Dock="Top"
             Height="130"
             SelectedValuePath="Key"
             SelectedValue="{Binding SelectedVal, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
             FontSize="18"
             Margin="0,0,0,20">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <DockPanel>
                    <TextBlock Text="{Binding Key, Mode=OneWay}" />
                    <TextBlock Text="{Binding Value, Mode=OneWay}" />
                </DockPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</DockPanel>

And the VM

public class NumericParameterPageViewModel : ActionSelectionPage
{
    private readonly Dictionary<string, IMyInterface> _valStorage = new Dictionary<string, IMyInterface>();
    private IMyInterface _selectedParameter;

    public ListBoxPage()
    {
    }

    public IMyInterface MyItem
    {
        get { return _selectedParameter; }
        set
        {
            SetProperty( ref _selectedParameter, value );
        }
    }

    public string SelectedVal
    {
        get
        {
            return _x;
        }
        set
        {
            SetProperty( ref _x, value );
            MyItem = _valStorage[ _x ];
        }
    }

    private string _x;

    public Dictionary<string, double> MyDict { get; } = new Dictionary<string, double>();

    public override void OnNavigatedTo(
        NavigationContext navigationContext )
    {
        var p = navigationContext.Parameters[ "ParameterList" ] as IMyInterface[];
        foreach (var item in p)
        {
            MyDict.Add( item.ID.Name, item.CurrentValue );
            _valStorage.Add( item.ID.Name, item );
        }
        SelectedItem = navigationContext.Parameters["ParamterID"] as IMyInterface;
        SelectedVal = MyDict.First().Key;
        base.OnNavigatedTo( navigationContext );
    }
}

All interface names here are made up, if two are slightly different (binding wise) it's because I cocked up manually changing them for the example.

Although it actually contains much more, for now assume IMyInterface just contains a string name, and a double value. (I apologize for the messy code / naming, still prototyping this)

Answer 1

You should set the Style (and not the ItemContainerStyle ) property to a ListBox style:

<Style x:Key="MyLbStyle" TargetType="{x:Type ListBox}">
    <Style.Resources>
        <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}"
                             Color="Yellow" />
        <SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightBrushKey }"
                             Color="Yellow" />
        <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}"
                             Color="Black" />
        <SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightTextBrushKey}"
                             Color="Black" />
    </Style.Resources>
</Style>

---

<ListBox ItemsSource="{Binding MyDict, Mode=OneWay}"
                         Style="{StaticResource MyLbStyle}"
                         DockPanel.Dock="Top"
                         SelectedValuePath="Key"
                         SelectedValue="{Binding SelectedVal, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <DockPanel>
                <TextBlock Text="{Binding Key, Mode=OneWay}" />
                <TextBlock Text="{Binding Value, Mode=OneWay}" />
            </DockPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>