How to setup a Style with Bindings in Code-Behind

[JakenVeina]

I've got the following style for laying out ViewModel items within a Grid, and I'm curious if there's a way I could set this up in code-behind, so I could just do the conversions inline, instead of having to create two whole IValueConverters.

<Style x:DataType="board:TileFormModel" Selector="ItemsControl > ContentPresenter">
    <Setter Property="Grid.Column" Value="{Binding Position.Column, Converter={x:Static board:ColumnIndexConverter.Instance}}" />
    <Setter Property="Grid.Row" Value="{Binding Position.Row, Converter={x:Static board:RowIndexConverter.Instance}}" />
</Style>

So far, I haven't had any other issues with doing proper bindings in code-behind, which I tend to prefer, as it's generally less verbose, and more type-safe.

[gehongyan]

I’m not sure what kind of conversion you performed in ColumnIndexConverter. The following example is just an assumption based on the information you provided.

---

Assuming the conversion logic you implemented in ColumnIndexConverter is as follows:

Func<int, int> conversion = x => x;

So, you can use C# in the code-behind to create a Style.

IValueConverter converter = new FuncValueConverter<int, int>(conversion);
Style style = new(x => x.OfType<ItemsControl>().Child().OfType<ContentPresenter>())
{
    Setters =
    {
        new Setter(
            Grid.ColumnProperty,
            new Binding("Position.Column") { Converter = converter }
        ),
        new Setter(
            Grid.RowProperty,
            new Binding("Position.Row") { Converter = converter }
        ),
    }
};

If you want to yield that converter, you can use compiled bindings to inline the conversion.

Style style = new(x => x.OfType<ItemsControl>().Child().OfType<ContentPresenter>())
{
    Setters =
    {
        new Setter(Grid.ColumnProperty, new CompiledBindingExtension(
            new CompiledBindingPathBuilder()
                .TypeCast<TileFormModel>()
                .Property(
                    new ClrPropertyInfo(
                        nameof(TileFormModel.Position.Column),
                        obj => ((TileFormModel) obj).Position.Column,
                        (obj, val) => ((TileFormModel) obj).Position.Column = val is int v ? conversion(v) : 0,
                        typeof(int)),
                    PropertyInfoAccessorFactory.CreateInpcPropertyAccessor
                ).Build())),
        new Setter(Grid.RowProperty, new CompiledBindingExtension(
            new CompiledBindingPathBuilder()
                .TypeCast<TileFormModel>()
                .Property(
                    new ClrPropertyInfo(
                        nameof(TileFormModel.Position.Row),
                        obj => ((TileFormModel) obj).Position.Row,
                        (obj, val) => ((TileFormModel) obj).Position.Row = val is int v ? conversion(v) : 0,
                        typeof(int)),
                    PropertyInfoAccessorFactory.CreateInpcPropertyAccessor
                ).Build())),
    }
};

---

Finally, add the style into your ItemsControl.

YourItemsControl.Styles.Add(style);

[JakenVeina]

Roger. I had everything there already, short of the CompiledBindingExtension code. I was hoping for something more direct like AvaloniaObject.Bind() but I wasn't really hold my breath. If that's the verbosity it takes, it's definitely more worth it to just do it in XAML.

Thanks for the input.