How can I setup my ASP.NET backend in IIS? - asp.net

Question

I am building a website that is managed over Microsoft IIS. I want my whole website to work like this:
The IIS gets a HTTP request over port 80 for the main website and then answers with the HTML and JS documents. These documents remain static and are simply saved as files on the server, which the IIS reads and send to the client without further modifying it.
In the JS document that the client gets, there are fetch()-commands that send additional requests during runtime over a different port when the user is interacting with the website. The browser should get back JSON data from the server. I have written a ASP.NET web application to do this.
This is what my current setup in IIS looks like:
enter image description here
I have set up a site for step one (front-end) and one for step two (back-end). I added a binding for the first site to port 80 and set the default document. I linked the second site to the directory in which the build binary of my ASP.NET application lies. Then, I added the binding with Port 5000 and the same IP-Address to the second site.
Step one works. When sending a request over Port 80, I get the website documents. But the second step doesn't. In debugging mode of Visual Studio, it works fine and it does it job. But I didn't manage to get step two working in IIS yet. The response I get when sending my requests is a 404. I created an additioonal controller to my back-end for testing that should just respond some hardcoded strings and do nothing more. Actually that works. I do get a 200 and the strings as a response. So there must be something wrong with the ASP.NET back-end communicating with my database.
I found out that everytime, when sending my request, an error log is written by my back-end. It says:
fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware1
An unhandled exception has occurred while executing the request.
System.Text.Json.JsonException: A possible object cycle was detected which is not supported. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 32.
at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_SerializerCycleDetected(Int32 maxDepth)
at System.Text.Json.JsonSerializer.Write(Utf8JsonWriter writer, Int32 originalWriterDepth, Int32 flushThreshold, JsonSerializerOptions options, WriteStack& state)
at System.Text.Json.JsonSerializer.WriteAsyncCore(Stream utf8Json, Object value, Type inputType, JsonSerializerOptions options, CancellationToken cancellationToken)
at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|27_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
at Microsoft.AspNetCore.Routing.EndpointMiddleware.g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware.g__Awaited|6_0(ExceptionHandlerMiddleware middleware, HttpContext context, Task task)
Again, I do not get the error when debugging the back-end ap
Can someone help?

Answer 1

The problem was basically wrong SQL Server permission setup. I managed to solve my problem. This may be helpful to people who are facing similar problems:
The "JsonException object cycle" error itself was not that helpful at all. So, I went into further debugging. I attached VisualStudio Debugging to the actual running IIS process like so: https://learn.microsoft.com/en-us/visualstudio/debugger/attach-to-running-processes-with-the-visual-studio-debugger?view=vs-2019
This was helpful for finding the reason for the error, as I could now experience log messages that were much more fitting to the actual error. Mind that you have to change the hostingModel to "outofprocess" in the web.config in order to attach to the standalone .Net process. https://learn.microsoft.com/en-us/aspnet/core/host-and-deploy/iis/out-of-process-hosting?view=aspnetcore-5.0
In case you are using SQL Server Management Studio, create a login for "NT Authority" (Object Explorer > Security > Logins > NT-Authority), grant access to your database and make sure that you do not select a "deny" role in user mapping, because I did so, and that was causing my error.