Почему контекст данных контекстного меню имеет значение null при первом открытии, но то, что ожидается при следующем открытии в WPF?

Поэтому, когда программа запускается и я щелкаю правой кнопкой мыши ListViewItem, отображается контекстное меню, но его DataContext не является объектом, связанным с ListViewItem, который я щелкнул. Вот почему эта привязка не работает и метод Convert конвертера не запускается:

<Image>
       <Image.Source>
              <Binding
               Path = "Process" Converter = "{StaticResource PriorityToIconConverter}"
                                    ConverterParameter = "{StaticResource RealTime}" />
        </Image.Source>
</Image>

Но когда я закрываю ContextMenu и открываю его снова, внезапно все работает нормально. Но почему не сразу после запуска программы?

У меня есть этот ListView:

<ListView Grid.Row = "1" x:Name = "ListView" Margin = "0,0,0,10"
                  ScrollViewer.CanContentScroll = "True"
                  ScrollViewer.VerticalScrollBarVisibility = "Auto"
                  ItemsSource = "{Binding ProcessInfos}"
                  Background = "#1a1a1a" Foreground = "#e0e0e0"
                  BorderBrush = "#333333" BorderThickness = "1"
                  SelectionMode = "Single"
                  SelectedItem = "{Binding SelectedProcessInfo, UpdateSourceTrigger=PropertyChanged}"
                  FontSize = "15">
            <ListView.Resources>
                <ControlTemplate x:Key = "CustomHeader" TargetType = "GridViewColumnHeader">
                    <Grid MinWidth = "50" Background = "{TemplateBinding Background}" Height = "40">
                        <TextBlock Background = "{TemplateBinding Background}" TextAlignment = "Center"
                                   Foreground = "{TemplateBinding Foreground}"
                                   Text = "{TemplateBinding Tag}" VerticalAlignment = "Center" />
                        <Thumb x:Name = "PART_HeaderGripper" HorizontalAlignment = "Right" Margin = "0" Width = "1" />
                    </Grid>
                </ControlTemplate>

                <Style TargetType = "GridViewColumnHeader">
                    <Style.Setters>
                        <Setter Property = "Background" Value = "#2b2b2b" />
                        <Setter Property = "Foreground" Value = "#e0e0e0" />
                        <Setter Property = "FontWeight" Value = "Bold" />
                        <Setter Property = "BorderBrush" Value = "#333333" />
                        <Setter Property = "BorderThickness" Value = "2" />
                        <Setter Property = "Padding" Value = "5" />
                    </Style.Setters>


                    <Style.Triggers>
                        <Trigger Property = "IsMouseOver" Value = "True">
                            <Setter Property = "Background" Value = "#3a3a3a" />
                            <Setter Property = "Foreground" Value = "#ffffff" />
                        </Trigger>
                        <Trigger Property = "IsPressed" Value = "True">
                            <Setter Property = "Background" Value = "#4a4a4a" />
                            <Setter Property = "Foreground" Value = "#e0e0e0" />
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </ListView.Resources>
            <ListView.View>
                <GridView d:DataContext = "{d:DesignInstance Type=models:ProcessInfo}">
                    <GridViewColumn Width = "200">
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <Grid Margin = "5">
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition Width = "Auto" />
                                        <ColumnDefinition />
                                    </Grid.ColumnDefinitions>
                                    <Border>
                                        <Image Source = "{Binding Icon}" Width = "20" Height = "20" />
                                    </Border>
                                    <TextBlock Grid.Column = "1" Text = "{Bindin gProcess.ProcessName}" />
                                </Grid>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                        <GridViewColumn.Header>
                            <GridViewColumnHeader Template = "{StaticResource CustomHeader}" Margin = "-3,0,0,0"
                                                  BorderThickness = "0" Tag = "Process Name" />
                        </GridViewColumn.Header>
                    </GridViewColumn>
                    <GridViewColumn Width = "100"
                                    DisplayMemberBinding = "{Binding Process.Id}">
                        <GridViewColumn.Header>
                            <GridViewColumnHeader Template = "{StaticResource CustomHeader}" Margin = "-3,0,0,0"
                                                  BorderThickness = "0" Tag = "PID" />
                        </GridViewColumn.Header>
                    </GridViewColumn>
                    <GridViewColumn Width = "180"
                                    DisplayMemberBinding = "{Binding MemoryUsage}">
                        <GridViewColumn.Header>
                            <GridViewColumnHeader Template = "{StaticResource CustomHeader}" Margin = "-3,0,0,0"
                                                  BorderThickness = "0" Tag = "Memory Usage" />
                        </GridViewColumn.Header>
                    </GridViewColumn>
                    <GridViewColumn Width = "180"
                                    DisplayMemberBinding = "{Binding CpuUsage}">
                        <GridViewColumn.Header>
                            <GridViewColumnHeader Template = "{StaticResource CustomHeader}" Margin = "-3,0,0,0"
                                                  BorderThickness = "0" Tag = "CPU Usage" />
                        </GridViewColumn.Header>
                    </GridViewColumn>
                    <GridViewColumn Width = "120"
                                    DisplayMemberBinding = "{Binding Process.Threads.Count}">
                        <GridViewColumn.Header>
                            <GridViewColumnHeader Template = "{StaticResource CustomHeader}" Margin = "-3,0,0,0"
                                                  BorderThickness = "0" Tag = "Thread Count" />
                        </GridViewColumn.Header>
                    </GridViewColumn>
                </GridView>
            </ListView.View>
        </ListView>

И это ContextMenu ListViewItem:

<ContextMenu x:Key = "MenuItemContextMenu" Opened = "ListViewItem_ContextMenuOpening" Background = "#1e1e1e" Foreground = "#e0e0e0" BorderBrush = "#4a4a4a"
                     d:DataContext = "{d:DesignInstance models:ProcessInfo}">
            <ContextMenu.Resources>

                <ControlTemplate x:Key = "MenuItemTemplate" TargetType = "MenuItem">
                    <Border Background = "{TemplateBinding Background}"
                            BorderBrush = "{TemplateBinding BorderBrush}"
                            BorderThickness = "0" Padding = "25 10">
                        <Grid>
                            <ContentPresenter ContentSource = "Header" HorizontalAlignment = "Left"
                                              VerticalAlignment = "Center" Margin = "5,0" />
                            <ContentPresenter x:Name = "Icon" ContentSource = "Icon"
                                              HorizontalAlignment = "Right"
                                              Width = "5"
                                              Height = "5"
                                              VerticalAlignment = "Center" Margin = "0 0 -10 0" />
                            <Popup x:Name = "SubMenuPopup" Placement = "Right"
                                   IsOpen = "{TemplateBinding IsSubmenuOpen}" Focusable = "False"
                                   PopupAnimation = "Fade">
                                <Border Background = "#1e1e1e" BorderBrush = "#4a4a4a"
                                        BorderThickness = "1">
                                    <StackPanel IsItemsHost = "True" KeyboardNavigation.DirectionalNavigation = "Cycle" />
                                </Border>
                            </Popup>
                        </Grid>
                    </Border>
                </ControlTemplate>

                <!-- Style for MenuItems -->
                <Style TargetType = "MenuItem">
                    <Setter Property = "Background" Value = "#1e1e1e" />
                    <Setter Property = "Foreground" Value = "#e0e0e0" />
                    <Setter Property = "Template" Value = "{StaticResource MenuItemTemplate}">
                    </Setter>
                    <Style.Triggers>
                        <Trigger Property = "IsMouseOver" Value = "True">
                            <Setter Property = "Background" Value = "#333333" />
                            <Setter Property = "Foreground" Value = "#ffffff" />
                        </Trigger>
                        <Trigger Property = "IsPressed" Value = "True">
                            <Setter Property = "Background" Value = "#444444" />
                            <Setter Property = "Foreground" Value = "#ffffff" />
                        </Trigger>
                        <Trigger Property = "IsSubmenuOpen" Value = "True">
                            <Setter Property = "Background" Value = "#333333" />
                        </Trigger>
                    </Style.Triggers>
                </Style>

                <diagnostics:ProcessPriorityClass x:Key = "RealTime">RealTime</diagnostics:ProcessPriorityClass>
                <diagnostics:ProcessPriorityClass x:Key = "High">High</diagnostics:ProcessPriorityClass>
                <diagnostics:ProcessPriorityClass x:Key = "AboveNormal">AboveNormal</diagnostics:ProcessPriorityClass>
                <diagnostics:ProcessPriorityClass x:Key = "Normal">Normal</diagnostics:ProcessPriorityClass>
                <diagnostics:ProcessPriorityClass x:Key = "BelowNormal">BelowNormal</diagnostics:ProcessPriorityClass>
                <diagnostics:ProcessPriorityClass x:Key = "Low">Idle</diagnostics:ProcessPriorityClass>

                <converters:PriorityToIconConverter x:Key = "PriorityToIconConverter" />

            </ContextMenu.Resources>

            <!-- Set Affinity -->
            <MenuItem Header = "Set affinity" />

            <!-- Set Priority with Submenu -->
            <MenuItem Header = "Set priority" x:Name = "MenuItem">
                <MenuItem Header = "Realtime" CommandParameter = "{StaticResource RealTime}">
                    <MenuItem.Icon>
                        <Image>
                            <Image.Source>
                                <Binding
                                    Path = "Process" Converter = "{StaticResource PriorityToIconConverter}"
                                    ConverterParameter = "{StaticResource RealTime}" />
                            </Image.Source>
                        </Image>
                    </MenuItem.Icon>
                </MenuItem>
                <MenuItem Header = "High" CommandParameter = "{StaticResource High}">
                    <MenuItem.Icon>
                        <Image>
                            <Image.Source>
                                <Binding
                                    Path = "Process" Converter = "{StaticResource PriorityToIconConverter}"
                                    ConverterParameter = "{StaticResource High}" />
                            </Image.Source>
                        </Image>
                    </MenuItem.Icon>
                </MenuItem>
                <MenuItem Header = "Above Normal" CommandParameter = "{StaticResource AboveNormal}">
                    <MenuItem.Icon>
                        <Image>
                            <Image.Source>
                                <Binding
                                    Path = "Process" Converter = "{StaticResource PriorityToIconConverter}"
                                    ConverterParameter = "{StaticResource AboveNormal}" />
                            </Image.Source>
                        </Image>
                    </MenuItem.Icon>
                </MenuItem>
                <MenuItem Header = "Normal" CommandParameter = "{StaticResource Normal}">
                    <MenuItem.Icon>
                        <Image>
                            <Image.Source>
                                <Binding
                                    Path = "Process" Converter = "{StaticResource PriorityToIconConverter}"
                                    ConverterParameter = "{StaticResource Normal}" />
                            </Image.Source>
                        </Image>
                    </MenuItem.Icon>
                </MenuItem>
                <MenuItem Header = "Below Normal" CommandParameter = "{StaticResource BelowNormal}">
                    <MenuItem.Icon>
                        <Image>
                            <Image.Source>
                                <Binding
                                    Path = "Process" Converter = "{StaticResource PriorityToIconConverter}"
                                    ConverterParameter = "{StaticResource BelowNormal}" />
                            </Image.Source>
                        </Image>
                    </MenuItem.Icon>
                </MenuItem>
                <MenuItem Header = "Low" CommandParameter = "{StaticResource Low}">
                    <MenuItem.Icon>
                        <Image>
                            <Image.Source>
                                <Binding
                                    Path = "Process" Converter = "{StaticResource PriorityToIconConverter}"
                                    ConverterParameter = "{StaticResource Low}" />
                            </Image.Source>
                        </Image>
                    </MenuItem.Icon>
                </MenuItem>
            </MenuItem>
        </ContextMenu>

        <Style TargetType = "ListViewItem">
            <Setter Property = "Background" Value = "#1e1e1e" />
            <Setter Property = "BorderBrush" Value = "#333333" />
            <Setter Property = "BorderThickness" Value = "0,0,0,1" />
            <Setter Property = "Padding" Value = "10" />
            <Setter Property = "Margin" Value = "0,0,0,5" />
            <Setter Property = "Foreground" Value = "#e0e0e0" />
            <Setter Property = "ContextMenu" Value = "{StaticResource MenuItemContextMenu}" />
            <!-- Hover and Selected States -->
            <Style.Triggers>
                <Trigger Property = "IsMouseOver" Value = "True">
                    <Setter Property = "Background" Value = "#333333" />
                    <Setter Property = "Foreground" Value = "#ffffff" />
                </Trigger>
                <Trigger Property = "IsSelected" Value = "True">
                    <Setter Property = "Background" Value = "#444444" />
                    <Setter Property = "Foreground" Value = "#ffffff" />
                </Trigger>
            </Style.Triggers>
        </Style>

Модель просмотра:

using System.Diagnostics;
using System.Windows;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using TaskManagerPlusPlus.Dialogs;
using TaskManagerPlusPlus.Models;
using TaskManagerPlusPlus.Services;
using TaskManagerPlusPlus.Views;
using Timer = System.Timers.Timer;

namespace TaskManagerPlusPlus.ViewModels;

public partial class TasksViewModel : BaseViewModel
{
    private readonly IProcessInfosManager _processInfosManager;
    [ObservableProperty] private ProcessInfosCollection _processInfos = [];
    [ObservableProperty] private ProcessInfo? _selectedProcessInfo;

    public TasksViewModel(IProcessInfosManager processInfosManager)
    {
        _processInfosManager = processInfosManager;
        
        RefreshProcesses();

        var timer = new Timer(1000)
        {
            AutoReset = true
        };

        timer.Elapsed += (_, _) => { RefreshProcesses(); };

        timer.Start();
    }

    private void RefreshProcesses()
    {
        var selectedProcessInfoProcessId = SelectedProcessInfo?.Process.Id;
        try
        {
            var processInfos = _processInfosManager.GetProcessInfos();

            ProcessInfos.Clear();
            foreach (var processInfo in processInfos)
            {
                ProcessInfos.Add(processInfo);
            }

            Application.Current.Dispatcher.Invoke(() =>
            {
                ProcessInfos.NotifyCollectionChanged();
                SelectedProcessInfo = ProcessInfos.FirstOrDefault(processInfo =>
                    processInfo.Process.Id == selectedProcessInfoProcessId);
            });
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
    }

    [RelayCommand]
    private void KillProcess()
    {
        SelectedProcessInfo?.Process.Kill();
    }

    [RelayCommand]
    private void StartProcess()
    {
        try
        {
            var startProcessDialog = new StartProcessDialog();
            var showDialog = startProcessDialog.ShowDialog();
            if (showDialog.HasValue && showDialog.Value)
            {
                var process = new Process
                {
                    StartInfo = new ProcessStartInfo(startProcessDialog.TaskLocation)
                    {
                        ErrorDialog = true
                    }
                };
                process.Start();
            }
        }
        catch (Exception)
        {
            MessageBox.Show("Process cannot be started.", "Process startup failure", MessageBoxButton.OK,
                MessageBoxImage.Error);
        }
    }
}

Я пробовал это:

public TasksView()
    {
        InitializeComponent();

        var timer = new Timer(2000) { AutoReset = true };

        

        timer.Elapsed += (_, _) =>
        {
            try
            {
                var listViewItem = (ListViewItem)ListView.ItemContainerGenerator.ContainerFromItem(ListView.Items[0]);
                Dispatcher.Invoke(() =>
                {
                    var contextMenu = listViewItem.ContextMenu!;
                    var menuItem = (MenuItem)((MenuItem)contextMenu.Items[1]!).Items[3]!;
                    Console.WriteLine(contextMenu.DataContext == null);
                });
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
        };

        timer.Start();
    }

Он показал, что при запуске программы контекст данных имеет значение null, но затем после закрытия и повторного открытия он показывает, что он не равен нулю.

Я также попробовал это:

private void TasksView_OnLoaded(object sender, RoutedEventArgs e)
    {
        var listViewItem = (ListViewItem)ListView.ItemContainerGenerator.ContainerFromItem(ListView.Items[0]);

        var contextMenu = listViewItem.ContextMenu!;
        contextMenu.IsOpen = true;
        contextMenu.IsOpen = false;
    }

Ничего не помогло.