CosmosDBTrigger Alters DateTimeOffset Format in Azure Function Isolated Process

[JarFrank]

I'm encountering an issue with the CosmosDBTrigger in an Azure Function using the isolated process model. When documents are triggered by changes in a Cosmos DB collection, the CosmosDBTrigger seems to alter the format of DateTimeOffset fields in the JSON payload.

Repro steps

Set up an Azure Function with a CosmosDBTrigger to monitor changes in a Cosmos DB collection.

public class TriggerFunction(ILoggerFactory loggerFactory)
{
    private readonly ILogger _logger = loggerFactory.CreateLogger<Function>();

    [Function("TriggerFunction")]
    public void Run([CosmosDBTrigger(
        databaseName: "my-database",
        containerName: "my-container",
        Connection = "ConnectionStrings:Cosmos",
        LeaseContainerName = "leases",
        StartFromBeginning = true,
        LeaseContainerPrefix = "my-",
        CreateLeaseContainerIfNotExists = true)] string input)
    {
        _logger.LogInformation("Migration {input}", input);
    }
}

1. Insert a document into the Cosmos DB collection:

{
    "id": "1",
    "TransactionDate": "2023-07-04T12:00:00+00:00"
}

2. The CosmosDBTrigger function receives:

{
    "id": "1",
    "TransactionDate": "2023-07-04T14:00:00+02:00"
}

Expected behavior

The CosmosDBTrigger should pass the document as-is without altering the format or values.

Actual behavior

The date field in the JSON document is modified.

Known workarounds

none.

Related information

• Azure Function 4.x - isolated process
• Language C#
• Packages: Microsoft.Azure.Functions.Worker, Version="1.22.0" Microsoft.Azure.Functions.Worker.Extensions.CosmosDB, Version="4.9.0" Microsoft.Azure.Functions.Worker.Extensions.Http, Version="3.2.0" Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore, Version="1.3.2" Microsoft.Azure.Functions.Worker.Sdk, Version="1.17.2" Microsoft.ApplicationInsights.WorkerService, Version="2.22.0" Microsoft.Azure.Functions.Worker.ApplicationInsights, Version="1.2.0"