feat: Improve filtering API

Author: DerekGooding

SimpleDataGrid.Example/MainViewModel.cs

@@ -1,4 +1,6 @@
 using SimpleDataGrid.Pagination;
+using System;
+using System.Collections.Generic;
 
 namespace SimpleDataGrid.Example;
 
@@ -24,10 +26,26 @@ private static List<Person> GetPeople()
 
     public void ApplyFilter(int minAge)
     {
-        People.ClearFilters();
-        People.AddFilter(p => p.Age >= minAge);
+        People.SetFilter("minAge", p => p.Age >= minAge);
+    }
+
+    public void ApplyMaxAgeFilter(int maxAge)
+    {
+        People.SetFilter("maxAge", p => p.Age <= maxAge);
     }
 
+    public void ApplyNameFilter(string namePrefix)
+    {
+        People.SetFilter("namePrefix", p => p.Name.StartsWith(namePrefix, StringComparison.OrdinalIgnoreCase));
+    }
+
+    public void RemoveFilter(string key)
+    {
+        People.RemoveFilter(key);
+    }
+
+    public IReadOnlyCollection<string> ActiveFilters => People.GetActiveFilters();
+
     public void ClearFilter()
     {
         People.ClearFilters();

SimpleDataGrid.Example/MainWindow.xaml

@@ -22,14 +22,36 @@
             <RowDefinition Height="Auto" />
         </Grid.RowDefinitions>
 
-        <StackPanel Grid.Row="0" Orientation="Horizontal" Margin="5">
-            <TextBox x:Name="SearchTextBox" Width="200" Margin="5" />
-            <Button Content="Search" Click="SearchButton_Click" Margin="5" />
-            <CheckBox x:Name="WildcardCheckBox" Content="Use Wildcards" VerticalAlignment="Center" Margin="5" />
-
-            <TextBox x:Name="MinAgeTextBox" Width="50" Margin="5" />
-            <Button Content="Filter by Min Age" Click="FilterButton_Click" Margin="5" />
-            <Button Content="Clear Filter" Click="ClearFilterButton_Click" Margin="5" />
+        <StackPanel Grid.Row="0" Orientation="Vertical" Margin="5">
+            <StackPanel Orientation="Horizontal">
+                <TextBox x:Name="SearchTextBox" Width="200" Margin="5" />
+                <Button Content="Search" Click="SearchButton_Click" Margin="5" />
+                <CheckBox x:Name="WildcardCheckBox" Content="Use Wildcards" VerticalAlignment="Center" Margin="5" />
+            </StackPanel>
+            <StackPanel Orientation="Horizontal">
+                <TextBox x:Name="MinAgeTextBox" Width="50" Margin="5" />
+                <Button Content="Filter by Min Age" Click="FilterButton_Click" Margin="5" />
+                <TextBox x:Name="MaxAgeTextBox" Width="50" Margin="5" />
+                <Button Content="Filter by Max Age" Click="MaxAgeFilterButton_Click" Margin="5" />
+                <TextBox x:Name="NamePrefixTextBox" Width="100" Margin="5" />
+                <Button Content="Filter by Name Prefix" Click="NamePrefixFilterButton_Click" Margin="5" />
+                <Button Content="Clear Filters" Click="ClearFilterButton_Click" Margin="5" />
+            </StackPanel>
+            <ItemsControl ItemsSource="{Binding People.ActiveFilters}">
+                <ItemsControl.ItemsPanel>
+                    <ItemsPanelTemplate>
+                        <StackPanel Orientation="Horizontal"/>
+                    </ItemsPanelTemplate>
+                </ItemsControl.ItemsPanel>
+                <ItemsControl.ItemTemplate>
+                    <DataTemplate>
+                        <StackPanel Orientation="Horizontal">
+                            <TextBlock Text="{Binding}" VerticalAlignment="Center" Margin="5,0"/>
+                            <Button Content="Remove" Click="RemoveFilterButton_Click" CommandParameter="{Binding}" Margin="5,0"/>
+                        </StackPanel>
+                    </DataTemplate>
+                </ItemsControl.ItemTemplate>
+            </ItemsControl>
         </StackPanel>
 
         <controls:PagedDataGrid x:Name="PagedDataGrid" Grid.Row="1" PagedSource="{Binding People}" AutoGenerateColumns="True" />

SimpleDataGrid.Example/MainWindow.xaml.cs

@@ -1,5 +1,6 @@
 using SimpleDataGrid.Controls;
 using System.Windows;
+using System.Windows.Controls;
 
 namespace SimpleDataGrid.Example;
 
@@ -60,4 +61,28 @@ private void GoToPageButton_Click(object sender, RoutedEventArgs e)
             viewModel.People.GoToPage(page);
         }
     }
+
+    private void MaxAgeFilterButton_Click(object sender, RoutedEventArgs e)
+    {
+        var viewModel = (MainViewModel)DataContext;
+        if (int.TryParse(MaxAgeTextBox.Text, out var maxAge))
+        {
+            viewModel.ApplyMaxAgeFilter(maxAge);
+        }
+    }
+
+    private void NamePrefixFilterButton_Click(object sender, RoutedEventArgs e)
+    {
+        var viewModel = (MainViewModel)DataContext;
+        viewModel.ApplyNameFilter(NamePrefixTextBox.Text);
+    }
+
+    private void RemoveFilterButton_Click(object sender, RoutedEventArgs e)
+    {
+        var viewModel = (MainViewModel)DataContext;
+        if (sender is Button button && button.CommandParameter is string key)
+        {
+            viewModel.RemoveFilter(key);
+        }
+    }
 }

SimpleDataGrid/Pagination/PagedCollection.cs

@@ -19,7 +19,7 @@ public class PagedCollection<T> : IPagedCollection, INotifyPropertyChanged
     private IReadOnlyList<T> _source = [];
     private IReadOnlyList<T> _filtered = [];
 
-    private readonly List<Func<T, bool>> _filters = [];
+    private readonly Dictionary<string, Func<T, bool>> _filters = [];
     private readonly List<(Func<T, object> selector, bool ascending)> _sorts = [];
     private Func<T, string>? _searchSelector;
     private string? _searchTerm;
@@ -35,6 +35,11 @@ public class PagedCollection<T> : IPagedCollection, INotifyPropertyChanged
     /// </summary>
     public event EventHandler? SortChanged;
 
+    /// <summary>
+    /// Occurs when the filter changes.
+    /// </summary>
+    public event EventHandler? FilterChanged;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="PagedCollection{T}"/> class.
     /// </summary>
@@ -61,17 +66,49 @@ public void SetSource(IReadOnlyList<T> items)
     /// <param name="filter">The filter to add.</param>
     public void AddFilter(Func<T, bool> filter)
     {
-        _filters.Add(filter);
+        SetFilter(Guid.NewGuid().ToString(), filter);
+    }
+
+    /// <summary>
+    /// Adds or updates a filter in the collection.
+    /// </summary>
+    /// <param name="key">The key of the filter.</param>
+    /// <param name="filter">The filter to add or update.</param>
+    public void SetFilter(string key, Func<T, bool> filter)
+    {
+        _filters[key] = filter;
         ApplyFiltering();
+        FilterChanged?.Invoke(this, EventArgs.Empty);
     }
 
+    /// <summary>
+    /// Removes a filter from the collection.
+    /// </summary>
+    /// <param name="key">The key of the filter to remove.</param>
+    public void RemoveFilter(string key)
+    {
+        if (_filters.Remove(key))
+        {
+            ApplyFiltering();
+            FilterChanged?.Invoke(this, EventArgs.Empty);
+        }
+    }
+
+    /// <summary>
+    /// Gets the keys of the active filters.
+    /// </summary>
+    /// <returns>A read-only collection of the active filter keys.</returns>
+    public IReadOnlyCollection<string> GetActiveFilters() => _filters.Keys;
+
+
     /// <summary>
     /// Clears all filters from the collection.
     /// </summary>
     public void ClearFilters()
     {
         _filters.Clear();
         ApplyFiltering();
+        FilterChanged?.Invoke(this, EventArgs.Empty);
     }
 
     /// <summary>
@@ -116,7 +153,7 @@ private void ApplyFiltering()
     {
         IEnumerable<T> query = _source;
 
-        foreach (var filter in _filters)
+        foreach (var filter in _filters.Values)
         {
             query = query.Where(filter);
         }