LeptonX Blazor ContentToolbar: ObjectDisposedException under Blazor Web App prerendering (event subscriptions never unsubscribed) #10730

3 Answer(s)

• 

  0

  AI-Bot created 3 months ago

  Support Team ABP Agent

  • Your analysis is correct for LeptonX 5.4.1: ContentToolbar subscribes to PageLayout change events in OnInitializedAsync using anonymous async lambdas and does not unsubscribe. Under Blazor Web App prerendering, those event continuations can run after the request DI scope is disposed, causing intermittent ObjectDisposedException. In interactive sessions, it also creates a subscription leak (component instances kept alive by the scoped PageLayout).

  • The safest/cleanest workaround today is exactly what you implemented: replace ContentToolbar with your own component that:

    1. does not subscribe during prerender (RendererInfo.IsInteractive == false), and
    2. implements IDisposable and unsubscribes using stored delegate fields (not anonymous lambdas).

  • Recommended implementation (matches your workaround, shown here as a self-contained “drop-in” replacement pattern):

  using System;
  using System.Collections.Specialized;
  using System.ComponentModel;
  using System.Threading.Tasks;
  using Volo.Abp.AspNetCore.Components.Web.LeptonXTheme.Components.ApplicationLayout.Common;
  using Volo.Abp.DependencyInjection;
  
  [ExposeServices(typeof(ContentToolbar))]
  [Dependency(ReplaceServices = true)]
  public class SafeContentToolbar : ContentToolbar, IDisposable
  {
      private bool _disposed;
      private NotifyCollectionChangedEventHandler? _collectionChanged;
      private PropertyChangedEventHandler? _propertyChanged;
  
      protected override Task OnInitializedAsync()
      {
          // IMPORTANT: do not call base.OnInitializedAsync() since it subscribes anonymous handlers.
          if (!RendererInfo.IsInteractive)
          {
              // Prerender snapshot: no need to listen; avoids continuations after request-scope disposal.
              return Task.CompletedTask;
          }
  
          _collectionChanged = async (_, _) =>
          {
              if (!_disposed)
              {
                  await RenderAsync();
              }
          };
  
          _propertyChanged = async (_, _) =>
          {
              if (!_disposed)
              {
                  await InvokeAsync(StateHasChanged);
              }
          };
  
          PageLayout.ToolbarItems.CollectionChanged += _collectionChanged;
          PageLayout.PropertyChanged += _propertyChanged;
  
          return Task.CompletedTask;
      }
  
      public void Dispose()
      {
          _disposed = true;
  
          if (_collectionChanged is not null)
          {
              PageLayout.ToolbarItems.CollectionChanged -= _collectionChanged;
          }
  
          if (_propertyChanged is not null)
          {
              PageLayout.PropertyChanged -= _propertyChanged;
          }
      }
  }
  

  • Apply the same pattern to any other LeptonX layout components that subscribe to PageLayout events (your stack trace also shows similar risk for components like Breadcrumbs).

  • If you want the “official” supported customization route: ABP documents replacing ContentToolbar via DI replacement (the exact approach you used with [ExposeServices] + [Dependency(ReplaceServices = true)]).

  Sources (validated):

  • https://abp.io/docs/latest/ui-themes/lepton-x/blazor
  • https://abp.io/docs/10.4/framework/ui/blazor/page-layout

  ---

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• 

  0

  maliming created 3 months ago

  Support Team Fullstack Developer

  Hi,

  The code matches your quote exactly in LeptonX Blazorise 5.4.0 / 5.4.1 / current dev — anonymous lambdas in ContentToolbar.OnInitializedAsync, no IDisposable. Your stack trace lines up — <<OnInitializedAsync>b__7_1>d.MoveNext() is the PropertyChanged lambda. The MudBlazor LeptonX ContentToolbar is already structured differently (implements IDisposable, named handlers, swallows ObjectDisposedException around the render call), so the fix shape on the Blazorise side is the same direction.

  On reproduction: the race didn't fire in our local Blazor Web App + InteractiveAuto + Blazorise LeptonX setup. The code path is unambiguous regardless, and your SafeContentToolbar is on the right pattern.

  Breadcrumbs in the same folder has the same bug — anonymous lambdas in OnInitializedAsync, no IDisposable. Two more LeptonX Blazorise menu components (ApplicationLayout/TopMenu/Navigation/MainMenuItem and PublicWebsiteLayout/Navigation/MainMenuItem) have a related leak: they wire PageLayout.PropertyChanged from OnParametersSet (so the handler re-adds on every render) and only unsubscribe NavigationManager.LocationChanged in Dispose. Slow leak rather than the crash you saw, but we'll cover them in the framework fix.

  Before we land the framework change, could you try this Breadcrumbs override next to your SafeContentToolbar and let us know whether the prerender ObjectDisposedException and the related unobserved-task log noise stop showing up?

  using System;
  using System.Collections.Specialized;
  using System.ComponentModel;
  using System.Threading.Tasks;
  using Microsoft.AspNetCore.Components;
  using Volo.Abp.AspNetCore.Components.Web.LeptonXTheme.Components.ApplicationLayout.Common;
  using Volo.Abp.DependencyInjection;
  
  namespace MyCompanyName.MyProjectName;
  
  [ExposeServices(typeof(Breadcrumbs))]
  [Dependency(ReplaceServices = true)]
  public class SafeBreadcrumbs : Breadcrumbs, IDisposable
  {
      private bool _disposed;
      private NotifyCollectionChangedEventHandler? _collectionChanged;
      private PropertyChangedEventHandler? _propertyChanged;
  
      protected override Task OnInitializedAsync()
      {
          // Skip base — its body wires the same unguarded lambdas this class replaces.
          if (!RendererInfo.IsInteractive)
          {
              return Task.CompletedTask;
          }
  
          _collectionChanged = async (_, _) =>
          {
              if (!_disposed)
              {
                  await InvokeAsync(StateHasChanged);
              }
          };
          _propertyChanged = async (_, _) =>
          {
              if (!_disposed)
              {
                  await InvokeAsync(StateHasChanged);
              }
          };
  
          PageLayout.BreadcrumbItems.CollectionChanged += _collectionChanged;
          PageLayout.PropertyChanged += _propertyChanged;
          return Task.CompletedTask;
      }
  
      public void Dispose()
      {
          _disposed = true;
  
          if (_collectionChanged is not null)
          {
              PageLayout.BreadcrumbItems.CollectionChanged -= _collectionChanged;
          }
  
          if (_propertyChanged is not null)
          {
              PageLayout.PropertyChanged -= _propertyChanged;
          }
      }
  }
  

  If running with SafeContentToolbar + SafeBreadcrumbs for a few days confirms the crash and the log noise go away on your side, we'll roll the same pattern into the LeptonX Blazorise components in the next release and cover the two MainMenuItem files at the same time.

  Thanks

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• 

  0

  maliming created 3 months ago

  Support Team Fullstack Developer

  Hi,

  The code matches your quote exactly in LeptonX Blazorise 5.4.0 / 5.4.1 / current dev — anonymous lambdas in ContentToolbar.OnInitializedAsync, no IDisposable. Your stack trace lines up — <<OnInitializedAsync>b__7_1>d.MoveNext() is the PropertyChanged lambda. The MudBlazor LeptonX ContentToolbar is already structured differently (implements IDisposable, named handlers, swallows ObjectDisposedException around the render call), so the fix shape on the Blazorise side is the same direction.

  On reproduction: the race didn't fire in our local Blazor Web App + InteractiveAuto + Blazorise LeptonX setup. The code path is unambiguous regardless, and your SafeContentToolbar is on the right pattern.

  Breadcrumbs in the same folder has the same bug — anonymous lambdas in OnInitializedAsync, no IDisposable. Two more LeptonX Blazorise menu components (ApplicationLayout/TopMenu/Navigation/MainMenuItem and PublicWebsiteLayout/Navigation/MainMenuItem) have a related leak: they wire PageLayout.PropertyChanged from OnParametersSet (so the handler re-adds on every render) and only unsubscribe NavigationManager.LocationChanged in Dispose. Slow leak rather than the crash you saw, but we'll cover them in the framework fix.

  Before we land the framework change, could you try this Breadcrumbs override next to your SafeContentToolbar and let us know whether the prerender ObjectDisposedException and the related unobserved-task log noise stop showing up?

  using System;
  using System.Collections.Specialized;
  using System.ComponentModel;
  using System.Threading.Tasks;
  using Microsoft.AspNetCore.Components;
  using Volo.Abp.AspNetCore.Components.Web.LeptonXTheme.Components.ApplicationLayout.Common;
  using Volo.Abp.DependencyInjection;
  
  namespace MyCompanyName.MyProjectName;
  
  [ExposeServices(typeof(Breadcrumbs))]
  [Dependency(ReplaceServices = true)]
  public class SafeBreadcrumbs : Breadcrumbs, IDisposable
  {
      private bool _disposed;
      private NotifyCollectionChangedEventHandler? _collectionChanged;
      private PropertyChangedEventHandler? _propertyChanged;
  
      protected override Task OnInitializedAsync()
      {
          // Skip base — its body wires the same unguarded lambdas this class replaces.
          if (!RendererInfo.IsInteractive)
          {
              return Task.CompletedTask;
          }
  
          _collectionChanged = async (_, _) =>
          {
              if (!_disposed)
              {
                  await InvokeAsync(StateHasChanged);
              }
          };
          _propertyChanged = async (_, _) =>
          {
              if (!_disposed)
              {
                  await InvokeAsync(StateHasChanged);
              }
          };
  
          PageLayout.BreadcrumbItems.CollectionChanged += _collectionChanged;
          PageLayout.PropertyChanged += _propertyChanged;
          return Task.CompletedTask;
      }
  
      public void Dispose()
      {
          _disposed = true;
  
          if (_collectionChanged is not null)
          {
              PageLayout.BreadcrumbItems.CollectionChanged -= _collectionChanged;
          }
  
          if (_propertyChanged is not null)
          {
              PageLayout.PropertyChanged -= _propertyChanged;
          }
      }
  }
  

  If running with SafeContentToolbar + SafeBreadcrumbs for a few days confirms the crash and the log noise go away on your side, we'll roll the same pattern into the LeptonX Blazorise components in the next release and cover the two MainMenuItem files at the same time.

  Thanks

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