# Appendix

## Errors

| Error message                                                                                                                                                             | Possible reason                                                         |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------- |
| **ODataException**: Invalid JSON. An unexpected comma was found in scope 'Object'. A comma is only valid between properties of an object or between elements of an array. | A comma appended to the last property of a JSON formatted request body. |

## General developer notes <a href="#general-developer-notes" id="general-developer-notes"></a>

### OData

* `IActionResult` is used when multiple return types are possible, otherwise `ActionResult<T>` can be used. The type property of `ProducesResponseTypeAttribute` can be excluded for `ActionResult<T>`.
* OData **functions** can only be `HttpGet`, OData **actions** can only be `HttpPost`.
* By protocol specification `enums` are serialized using the enum member's *string*, not its *value*.
* [Routing conventions](https://learn.microsoft.com/en-us/odata/webapi/built-in-routing-conventions) (only partly applicable for AspNetCore.OData v.8).
* [$ref](https://learn.microsoft.com/en-us/aspnet/web-api/overview/odata-support-in-aspnet-web-api/odata-v4/entity-relations-in-odata-v4#creating-a-relationship-between-entities) is not supported.
* Reasonably accurate OData [examples](https://github.com/dotnet/aspnet-api-versioning/tree/93bd8dc7582ec14c8ec97997c01cfe297b085e17/examples/AspNetCore/OData).

### [Swashbuckle](https://github.com/domaindrivendev/Swashbuckle.AspNetCore)

* Explicit `From` parameter bindings are required, otherwise *Swashbuckle* will describe them as query parameters by default. Code comments of parameters decorated with `FromForm` do not show up ([#2519](https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/2519)).


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://dev.smartstore.com/framework/web-api/appendix.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.