Handle Azure Function input binding error - error-handling

Question

I have an Azure Function (version 4, with C# on .NET 6) that uses Cosmos DB input binding.
When the Cosmos DB input is querying for a document that does not exist it returns HTTP 404 response, however the Azure Function itself does not propagate this response and actually returns a HTTP 500 response.
How do I catch the Cosmos DB response to be able to act accordingly in the Azure function?
Or in other words - how do I perform error/http-response handling on the function's input bindings?
I hoped validating that the input argument is not null would be it,
and also tried to validate that the IEnumerable response is not empty,
but it turns out it doesn't even enter the code in the function when it gets the Cosmos DB 404 response. The function just breaks and the returns HTTP 500:
[FunctionName("GetItems")]
public IActionResult GetItems(
[HttpTrigger(AuthorizationLevel.Function, "get", Route = null)] HttpRequest req,
[CosmosDB(
databaseName: "my-db",
containerName: "my-container",
Connection = "my-conn-string",
PartitionKey = "my-pk")] IEnumerable<MyItem> items)
{
_logger.LogInformation("Get list of items");
if (items == null)
{
_logger.LogInformation("Items object is null");
return new NotFoundResult();
}
var itemsList = items as List<MyItem>;
if (itemsList.Count == 0)
{
_logger.LogInformation("Items object is missing");
return new NotFoundResult();
}
return new OkObjectResult(itemsList.First());
}
}

Answer 1

Below is the example of input binding error.
[FunctionName("EventHubTrigger")]
[FixedDelayRetry(5, "00:00:10")]
public static async Task Run([EventHubTrigger("myHub", Connection = "EventHubConnection")] EventData[] events, ILogger log)
{
// ...
}
and Here is the complete documentation on Handling binding errors.