回答編集履歴

  理由はさっぱりわかりませんが、`SampleInfos`を**更新する前**に`SelectedInfo`を`null`にしておくと動作するようになりました。

 

  確認した簡略コード

  <Window

  x:Class="Questions377285.MainWindow"

  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

  xmlns:local="clr-namespace:Questions377285"

  Width="800"

  Height="450">

  <Window.DataContext>

  <local:ContentGridViewModel />

  </Window.DataContext>

  <Grid>

  <Grid.RowDefinitions>

  <RowDefinition Height="Auto" />

  <RowDefinition Height="Auto" />

  <RowDefinition />

  </Grid.RowDefinitions>

  <Button Command="{Binding Command}" Content="UIスレッド Update" />

  <ComboBox

  Grid.Row="1"

  DisplayMemberPath="TestNumber"

  ItemsSource="{Binding SampleInfos}"

  SelectedItem="{Binding SelectedInfo.Value}" />

  <ListBox

  Grid.Row="2"

  DisplayMemberPath="TestNumber"

  ItemsSource="{Binding SampleInfos}"

  SelectedItem="{Binding SelectedInfo.Value}" />

  </Grid>

  </Window>

  ```

 

  using System;

  using System.Collections.Generic;

  using System.Collections.ObjectModel;

  using System.Linq;

  using System.Reactive.Subjects;

  using System.Threading.Tasks;

  using System.Windows;

  using System.Windows.Data;

  using Reactive.Bindings;

 

  namespace Questions377285

  {

  public class SampleInfo

  {

  public int TestNumber { get; set; }

  public bool IsSelected { get; set; }

  }

 

  public class ContentGridViewModel

  {

  public ObservableCollection<SampleInfo> SampleInfos { get; } = new()

  {

  new() { TestNumber = 1, },

  new() { TestNumber = 2, },

  new() { TestNumber = 3, },

  };

  public ReactivePropertySlim<SampleInfo?> SelectedInfo { get; } = new();

  public ReactiveCommand Command { get; } = new();

 

  private readonly Subject<bool> InfoSubject = new();

 

  public ContentGridViewModel()

  {

  BindingOperations.EnableCollectionSynchronization(SampleInfos, new());

 

  SelectedInfo.Subscribe(o =>

  {

  foreach (var info in SampleInfos)

  {

  info.IsSelected = info.TestNumber == o?.TestNumber;

  }

  });

 

  InfoSubject.Subscribe(o => ReceiveInfo());

 

  Command.Subscribe(ReceiveInfo);

 

  _ = Task.Run(async () =>

  {

  while (true)

  {

  await Task.Delay(TimeSpan.FromSeconds(5));

  InfoSubject.OnNext(true);

  }

  });

  }

 

  private void ReceiveInfo()

  {

  var selectedInfo = SelectedInfo.Value;

  // ＊＊＊＊＊＊＊＊＊ココ

  SelectedInfo.Value = null;

 

  SampleInfoListUpdate(Get());

 

  SelectedInfo.Value = SampleInfos.FirstOrDefault(o => o.TestNumber == selectedInfo?.TestNumber);

  }

 

  private List<SampleInfo> Get()

  => Enumerable.Range(1, SampleInfos.Count + 1)

  .Select(x => new SampleInfo { TestNumber = x, })

  .ToList();

 

  private void SampleInfoListUpdate(List<SampleInfo> list)

  {

  SampleInfos.Clear();

  foreach (var info in list)

  {

  SampleInfos.Add(info);

  }

  }

  }

 

  public partial class MainWindow : Window

  {

  public MainWindow() => InitializeComponent();

  }

  }

  ```