ASP.NET Core Logging Integration File Not Found Exception

[bradleyables22]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Hope I've tagged this correctly, apologies if incorrect.

When updating an ap from .NET 8 to .NET10, after deployment to Azure App Services the following log started showing up in Application Insights.

Startup assembly Microsoft.AspNetCore.AzureAppServices.HostingStartup failed to execute. See the inner exception for more details. Could not load file or assembly 'Microsoft.AspNetCore.AzureAppServices.HostingStartup, Culture=neutral, PublicKeyToken=null'. The system cannot find the file specified.

Logging Integration Extension in AAS has been updated to 10.0.5. Application is running latest .NET 10 distro. This issue appears in both self-contained and framework dependent.

Expected Behavior

Exception is not thrown at application startup in hosting environment.

Steps To Reproduce

deploy an asp.net api to azure app services with App insights telemetry enabled.

Exceptions (if any)

System.InvalidOperationException: System.IO.FileNotFoundException:   at System.Reflection.RuntimeAssembly.InternalLoad (System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)   at System.Reflection.Assembly.Load (System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e)   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.ExecuteHostingStartups (Microsoft.AspNetCore.Hosting, Version=10.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60)

.NET Version

10.0.201

Anything else?

Thanks for all yall do.

[github-actions]

Triage Summary

Area: area-hosting (the error originates in GenericWebHostBuilder.ExecuteHostingStartups within Microsoft.AspNetCore.Hosting, and the failing component Microsoft.AspNetCore.AzureAppServices.HostingStartup lives under src/Azure/AzureAppServicesIntegration which is part of the hosting area)
Type: bug (a FileNotFoundException is thrown at startup on Azure App Services after upgrading to .NET 10, which is clearly broken behavior)

Regression Info

• Previously working version: .NET 8
• Broken since: .NET 10 (SDK 10.0.201)
• The Microsoft.AspNetCore.AzureAppServices.HostingStartup assembly cannot be found at runtime when deploying to Azure App Services with .NET 10, both in self-contained and framework-dependent deployment modes. The Azure Logging Integration site extension has been updated to 10.0.5 but the assembly still cannot be loaded.

Potential Duplicates

• Startup assembly Microsoft.AspNetCore.AzureAppServices.HostingStartup failed to execute in Azure App service. #48442 - "Startup assembly Microsoft.AspNetCore.AzureAppServices.HostingStartup failed to execute in Azure App service." (similarity: high — identical exception, same component, same Azure App Services context; that issue was for .NET 7)
• Logging site extension should use startup hooks (instead of additional deps) #34864 - "Logging site extension should use startup hooks (instead of additional deps)" (similarity: medium — describes the root cause of this recurring issue: the DOTNET_ADDITIONAL_DEPS-based approach requires manual updates for each new TFM)

Notes

• This appears to be a recurring pattern: each time a new .NET major version is released, the Azure App Services logging site extension fails to load the hosting startup assembly. Issue Logging site extension should use startup hooks (instead of additional deps) #34864 tracks a structural fix (switching to startup hooks) that would prevent this class of regression entirely.
• The Azure App Services site extension team may also need to be notified to deploy an updated extension for .NET 10.
• The reporter notes this affects both self-contained and framework-dependent deployments, which is consistent with the DOTNET_ADDITIONAL_DEPS-based mechanism failing for the new TFM.

Generated by Issue Triage Agent for dotnet/aspnetcore for issue #66315 · ● 176.7K · ◷