CollectionViewSource with custom sort - wpf

Question

I'm new to WPF and I'm having difficulty trying to sort a CollectionViewSource with a custom sort. Here's the situation:
I have a SearchView that is called with a parameter which becomes it's datacontext like so:
mainView.SetGlobalOverlay(New SearchView With {.DataContext = interventionViewModel})
In the SearchView.xaml, I then bind the CollectionViewSource to the collection :
<CollectionViewSource x:Key="UnitsCollection"
Filter="UnitsCollection_Filter"
Source="{Binding Path=Units}" />
Now, I already have an IComparer interface implemented in another shared class. This comparer is used on a ListCollectionView somewhere else in the sourcecode and works fine. Now, how can I re-use this comparer on a CollectionViewSource?

Answer 1

In order to use the custom sorter for the CollectionViewSource, you have to wait until the ItemsControl (e.g. a list box) is loaded; then you can get the ListCollectionView using the View property of the CollectionViewSource.
As illustration, here is a small example that displays a list of integers in two different ways: the upper list box applies a custom sort order, whereas the lower list box is unsorted:
MainWindow.xaml:
<Window x:Class="WpfApplication27.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:clr="clr-namespace:System;assembly=mscorlib"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="300">
<Window.Resources>
<CollectionViewSource x:Key="MyCollectionViewSource1" Source="{Binding RawData}" />
<CollectionViewSource x:Key="MyCollectionViewSource2" Source="{Binding RawData}" />
</Window.Resources>
<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<ListBox Grid.Row="0" Margin="5" Background="LightSkyBlue"
ItemsSource="{Binding Source={StaticResource MyCollectionViewSource1}}"/>
<ListBox Grid.Row="1" Margin="5" Background="LightYellow"
ItemsSource="{Binding Source={StaticResource MyCollectionViewSource2}}"/>
</Grid>
</Window>
MainWindow.xaml.cs:
using System.Collections;
using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Data;
namespace WpfApplication27
{
public partial class MainWindow : Window
{
public ObservableCollection<int> RawData { get; private set; }
public MainWindow()
{
RawData = new ObservableCollection<int> { 10, 222, 1, 333, 2, 777, 6 };
InitializeComponent();
DataContext = this;
this.Loaded += MainWindow_Loaded;
}
void MainWindow_Loaded(object sender, RoutedEventArgs e)
{
CollectionViewSource source = (CollectionViewSource)(this.Resources["MyCollectionViewSource1"]);
ListCollectionView view = (ListCollectionView)source.View;
view.CustomSort = new CustomSorter();
}
}
// Sort by number of digits (descending), then by value (ascending)
public class CustomSorter : IComparer
{
public int Compare(object x, object y)
{
int digitsX = x.ToString().Length;
int digitsY = y.ToString().Length;
if (digitsX < digitsY)
{
return 1;
}
else if (digitsX > digitsY)
{
return -1;
}
return (int) x - (int) y;
}
}
}

Answer 2

This worked really good for me. My scenario is that I have rarely more than 10 - 15 groups. I keep a int value, lets call it "Order". I use this to show the int value on the expander. I then have a string value, lets call it "SortOrder" which is what I load into my SortDesceription.
SortOrder = SortDefinition(Order);
public static string SortDefinition(int? value)
{
if (value is null)
return string.Empty;
if (value > 90)
return "ZZZZZ";
return
$"AAAA{((char)value + 65)
.ToString()}";
}