xaml-csharp-development-skill-for-avalonia

WPF CollectionView Group/Sort/Filter to Avalonia Patterns

Table of Contents

1. Scope and APIs
2. Collection Shaping Mapping
3. Conversion Example
4. Avalonia C# Equivalent
5. Troubleshooting

Scope and APIs

Primary WPF APIs:

• CollectionViewSource
• ICollectionView sorting/filtering/grouping

Primary Avalonia patterns:

• view-model projection lists for filter/sort/group state
• item controls (ListBox, TreeView, optional external DataGrid package)
• explicit query state in view-models instead of implicit view-side filters

Collection Shaping Mapping

WPF	Avalonia
CollectionViewSource.View.Filter	view-model predicate and projected collection
SortDescriptions	view-model sort state and projected ordering
grouping in CollectionView	grouped view-model collections + templates

Conversion Example

WPF C#:

CollectionView view = (CollectionView)CollectionViewSource.GetDefaultView(Items);
view.Filter = item => ((Customer)item).IsActive;
view.SortDescriptions.Add(new SortDescription(nameof(Customer.Name), ListSortDirection.Ascending));

Avalonia XAML:

<StackPanel xmlns="https://github.com/avaloniaui"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:vm="using:MyApp.ViewModels"
            x:DataType="vm:CustomersViewModel"
            Spacing="8">
  <TextBox Watermark="Filter" Text="{CompiledBinding Query, Mode=TwoWay}" />
  <ListBox ItemsSource="{CompiledBinding VisibleCustomers}" />
</StackPanel>

Avalonia C# Equivalent

using System;
using System.Collections.ObjectModel;
using System.Linq;

public sealed class CustomersViewModel
{
    public ObservableCollection<Customer> AllCustomers { get; } = new();
    public ObservableCollection<Customer> VisibleCustomers { get; } = new();

    public void Refresh(string query)
    {
        var filtered = AllCustomers
            .Where(x => x.IsActive)
            .Where(x => string.IsNullOrWhiteSpace(query) || x.Name.Contains(query, StringComparison.OrdinalIgnoreCase))
            .OrderBy(x => x.Name)
            .ToList();

        VisibleCustomers.Clear();
        foreach (var item in filtered)
            VisibleCustomers.Add(item);
    }
}

Troubleshooting

1. Filtering logic spread across view and model.
   • keep sort/filter state explicit in view-model properties.
2. grouping output is unstable.
   • model groups as explicit objects and template them directly.
3. very large collections stutter on every keystroke.
   • debounce query updates and reduce full-collection recomputation.

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