Our Azure App Service fails to start with below error: Could not load file or assembly 'System.Diagnostics.DiagnosticSource

zhuq 11

Our Azure App Service fails to start with below error:

Could not load file or assembly 'System.Diagnostics.DiagnosticSource, Version=4.0.4.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The system cannot find the file specified.

We followed a few recommended solution by the community and attempted to run the website by turning off the 'app insight', when this solution is applied, the error disappears but the website doesn't load. but if we turn it back on, the error reappears.

we are using .NET Framework 4.7.2 web application.

Ref

https://github.com/microsoft/ApplicationInsights-aspnetcore/issues/1008

https://windows-hexerror.linestarve.com/q/so67600522-when-installing-application-insights-it-keeps-complaining-about-diagnosticsource-package-version

https://learn.microsoft.com/en-us/azure/azure-monitor/app/web-app-extension-release-notes

your help will be appreciated

2 answers

VenkateshDodda-MSFT 22,401 Reputation points Microsoft Employee

2022-10-06T07:51:22.887+00:00
@zhuq Thank you for reaching out to Microsoft Q&A. Apologize for the inconvenience caused on this.

Can you check the contents of the \bin folder for hosted web app. If you do NOT have System.Runtime.CompilerServices.Unsafe.dll in bin folder, then try to remove the <bindingRedirect/> setting from the web.config file and then the app will pick up the newer version that our extension brings.

If you don't want to remove the <bindingRedirect/> setting then please try changing the binding redirect version in your web.config file in your app service to below

<dependentAssembly> <assemblyIdentity name="System.Diagnostics.DiagnosticSource" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" /> <bindingRedirect oldVersion="0.0.0.0-4.0.4.1" newVersion="4.0.4.1"/> </dependentAssembly>

if you have file System.Runtime.CompilerServices.Unsafe.dll in your \bin folder, then as a workaround, you can revert to the older App Insights extension version by going into App Service settings and manually set ApplicationInsightsAgent_EXTENSION_VERSION = 2.8.43

Feel free to reach back to me if you have any questions on this.
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Nelson Hernandez 20 Reputation points

2023-11-22T08:41:50.2133333+00:00

Hi @VenkateshDodda-MSFT I'm encountering a similar problem, but with a more recent version. I receive an error stating "System.Diagnostics.DiagnosticSource, Version=6.0.0.0," although Azure.Core utilizes version 6.0.0.1. When I downgrade my NuGet package from 6.0.0.1 to 6.0.0.0, I encounter a different error: "Could not load file or assembly 'System.Diagnostics.DiagnosticSource, Version=4.0.4.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'." Attempting to switch from version 6.0.0.0 to 4.0.4.0 results in a compatibility issue with "Azure.Core" and "Azure.Storage.Blobs," which do not support System.Diagnostics.DiagnosticSource, Version=4.0.4.0. Despite having consistent references to version 6.0.0.1 in both my web.config and the app.config of my new DLL, the error persists.

=== Pre-bind state information === LOG: DisplayName = System.Diagnostics.DiagnosticSource, Version=6.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51 (Fully-specified) LOG: Appbase = file:///D:/System/testsystem/ LOG: Initial PrivatePath = D:\System\testsystem\bin Calling assembly : Azure.Storage.Blobs, Version=12.19.1.0, Culture=neutral, PublicKeyToken=92742159e12e44c8.

LOG: This bind starts in default load context. LOG: Using application configuration file: D:\System\testsystem\web.config LOG: Using host configuration file: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet.config LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework64\v4.0.30319\config\machine.config. LOG: Post-policy reference: System.Diagnostics.DiagnosticSource, Version=6.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51 LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/root/4a4892e4/1a9eb44/System.Diagnostics.DiagnosticSource.DLL. WRN: Comparing the assembly name resulted in the mismatch: Revision Number ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated. DATE/TIME: 11/21/2023 10:53:57 PM

Nelson Hernandez 20 Reputation points

2023-11-22T11:00:11.83+00:00

I'm encountering a similar problem, but with a more recent version. I receive an error stating "System.Diagnostics.DiagnosticSource, Version=6.0.0.0," although Azure.Core utilizes version 6.0.0.1. When I downgrade my NuGet package from 6.0.0.1 to 6.0.0.0, I encounter a different error: "Could not load file or assembly 'System.Diagnostics.DiagnosticSource, Version=4.0.4.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'." Attempting to switch from version 6.0.0.0 to 4.0.4.0 results in a compatibility issue with "Azure.Core" and "Azure.Storage.Blobs," which do not support System.Diagnostics.DiagnosticSource, Version=4.0.4.0. Despite having consistent references to version 6.0.0.1 in both my web.config and the app.config of my new DLL, the error persists. <dependentAssembly> <assemblyIdentity name="System.Diagnostics.DiagnosticSource" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" /> <bindingRedirect oldVersion="0.0.0.0-6.0.0.1" newVersion="6.0.0.1" /> </dependentAssembly> === Pre-bind state information === LOG: DisplayName = System.Diagnostics.DiagnosticSource, Version=6.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51 (Fully-specified) LOG: Appbase = file:///D:/System/testsystem/ LOG: Initial PrivatePath = D:\System\testsystem\bin Calling assembly : Azure.Storage.Blobs, Version=12.19.1.0, Culture=neutral, PublicKeyToken=92742159e12e44c8. LOG: This bind starts in default load context. LOG: Using application configuration file: D:\System\testsystem\web.config LOG: Using host configuration file: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet.config LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework64\v4.0.30319\config\machine.config. LOG: Post-policy reference: System.Diagnostics.DiagnosticSource, Version=6.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51 LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/root/4a4892e4/1a9eb44/System.Diagnostics.DiagnosticSource.DLL. WRN: Comparing the assembly name resulted in the mismatch: Revision Number ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated. DATE/TIME: 11/21/2023 10:53:57 PM
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Maciej Skierski 0 Reputation points

2023-11-28T00:10:22.2666667+00:00
I'm not sure if this is going to help anyone but I had the same issue when instrumenting an old web site. I traced this to a tag in web.config

<assemblyBinding appliesTo="v2.0.50727" xmlns="urn:schemas-microsoft-com:asm.v1">

After removing ****appliesTo **** attribute, dll redirection and load started to worked.
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Our Azure App Service fails to start with below error: Could not load file or assembly 'System.Diagnostics.DiagnosticSource

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