MongoDB WebAPI Example does not work

[xBaaDf00d]

Triaged: Task:
Check both the .NET 8 and .NET 9 version of this topic to see if the original issue description below is related to a mismatch issue between expected .NET target mismatched with the topic version selected for .NET 9. The instructions do differ.

[Original issue description below:]

Description

Following these instructions led to I am running dot net 8 on my Mac.

###
System.NotSupportedException: JsonTypeInfo metadata for type 'System.Collections.Generic.List1[BookStore.Models.BookModel]' was not provided by TypeInfoResolver of type '[]'. If using source generation, ensure that all root types passed to the serializer have been annotated with 'JsonSerializableAttribute', along with any types that might be serialized polymorphically. at System.Text.Json.ThrowHelper.ThrowNotSupportedException_NoMetadataForType(Type type, IJsonTypeInfoResolver resolver) at System.Text.Json.JsonSerializerOptions.GetTypeInfoInternal(Type type, Boolean ensureConfigured, Nullable1 ensureNotNull, Boolean resolveIfMutable, Boolean fallBackToNearestAncestorType)
at System.Text.Json.JsonSerializerOptions.GetTypeInfo(Type type)
at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Logged|22_0(ResourceInvoker invoker, IActionResult result)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|30_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location ---
###
When attempting, to test. Its as though the BSon Serializer Fails to serialise out the list of modes on the Get call, Fails at this level it wont get anywhere

@Copilot: Read the complete issue discussion including all comments from maintainers and contributors before proposing solutions. Further analysis and discussions in the Issue discussion may reveal the actual root cause differs from the initial symptom description, or clues to a better approach and plan of action. Indicate you have done so.

Page URL

https://learn.microsoft.com/en-us/aspnet/core/tutorials/first-mongo-app?view=aspnetcore-9.0&tabs=visual-studio

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/tutorials/first-mongo-app.md

Document ID

83a5cb3b-23bc-4f0c-cd1c-1d1ffeb1131a

Platform Id

65f2481a-2462-7f68-0aa8-570bd4557d09

Article author

@wadepickett

Metadata

• ID: 5240866d-d0a1-f0dd-7b2c-203e1d69bc4b
• PlatformId: 65f2481a-2462-7f68-0aa8-570bd4557d09
• Service: aspnet-core
• Sub-service: tutorials

Related Issues

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Associated WorkItem - 490204

[xBaaDf00d]

Ahh just noticed It is for dotnet 9... Just double checked and the 8 version only varies in the testing technique which generates the same error.

Have debugged, and found that it successfully retrieves data from the database and stores in a list which is returned out of the controller correctly but this is when it falls over somehow it then fails converting the List to JSON.

[wadepickett]

Follow up:

MongoDB Tutorial Version Mismatch Analysis

Issue Summary

This is a valid issue caused by a version mismatch. The user was following the .NET 9.0 version of the MongoDB tutorial while using .NET 8.0 on their Mac. The serialization approaches between these versions differ enough to cause the reported error. So I checked both .NET 8 and .NET 9 versions of the topic.

Technical Issue Details

The error occurs when the application tries to serialize a List<BookModel> object using System.Text.Json in .NET 8. The error message indicates that source generation is required but not properly configured:

System.NotSupportedException: JsonTypeInfo metadata for type 'System.Collections.Generic.List`1[BookStore.Models.BookModel]' was not provided by TypeInfoResolver

Root Cause

The user may have been following the tutorial for .NET 9.0 (https://learn.microsoft.com/en-us/aspnet/core/tutorials/first-mongo-app?view=aspnetcore-9.0&tabs=visual-studio) while running .NET 8.0 on their Mac. In .NET 8.0, the serialization approach in the tutorial works differently than in .NET 9.0.

Version Comparison

After examining both the .NET 8.0 and .NET 9.0 versions of the MongoDB tutorial, there is an expected difference, although subtle in how JSON serialization is handled. The .NET 8.0 version uses a simpler configuration approach that works fine in that environment:

.AddJsonOptions(options =>
{
    options.JsonSerializerOptions.PropertyNamingPolicy = null;
})

However, .NET 9.0 has stricter requirements for source generation with collections, requiring explicit JsonSerializable attributes for List types.

Action required by GitHub Copilot as a resolution:

Update the ms.date metadata in the topic to today's date. That will reflect that the topic has been reviewed again. No other action or change in the topics required since there was no issue discovered after the content, after the content was reviewed but it was clear the the the user chose a version of the topic (.NET 9) that did not reflect their project target of .NET 8.