Fix Application Pool Conflicts on IIS

When hosting a web application on IIS, you may encounter HTTP Error 500.35: “ASP.NET Core does not support multiple apps in the same app pool.” This error typically occurs when you try to run two or more ASP.NET Core applications in the same application pool. This issue can be frustrating, especially if you are not aware of the boundaries that lead to this issue.

Cause of the problem
ASP.NET Core applications have specific hosting requirements, especially when running on IIS. Unlike traditional ASP.NET applications, ASP.NET Core restricts you from running multiple applications within the same application pool. The root cause of HTTP Error 500.35 lies in the way ASP.NET Core manages dependencies and the runtime environment. When multiple applications share the same app pool, each application attempts to initialize and manage its own version of the .NET runtime, which can lead to instability and crashes.

way out

To work around this issue, you can assign a separate application pool by following these steps:
• Open IIS Manager.
• In the Connections pane, expand the server node and click Application Pools.
• Right-click an existing application pool or select Add Application Pool to create a new application pool.
• Assign each ASP.NET Core application its own dedicated application pool. If you use the out-of-process hosting model, ensure that the .NET CLR version is set to “No Managed Code.”
• To associate each application with its own application pool, right-click the application, select Application Management > Advanced Settings, and then select the appropriate application pool.

This should fix the issue. You can also check the event log and stdout log to see where and why it’s failing.

System Event Log

• Open Event Viewer on the server.

• Go to Windows Logs > System to review any error messages or warnings that indicate why the application did not start.

Standard output logging

• Navigate to the root directory of your ASP.NET Core application.

• Open the web.config file in a text editor.

• Locate the aspNetCore element and set stdoutLogEnabled=”true” and specify the path to the stdoutLogFile. For example: