I have a simple Azure Functions app, which includes HTTP trigger and a durable orchestration function, which the trigger invokes. This app runs fine when tested locally, but fails when it runs on Azure. The error coming from the orchestrator function is:

07-df83-4d2d-8023-ad4da1eed437, Duration=107ms)Unable to cast object of type 'System.String' to type 'Microsoft.Azure.WebJobs.Extensions.DurableTask.IDurableOrchestrationContext'.

Here is the code for the HTTP trigger:

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.DurableTask;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;

public static class DurableHttpStart
{
    [FunctionName("DurableHttpStart")]
    public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequest req,
        [DurableClient] IDurableOrchestrationClient starter,
        ILogger log)
    {
        // Function input comes from the request content.
        string instanceId = await starter.StartNewAsync("OrchestratorFunction", null);

        log.LogInformation($"Started orchestration with ID = '{instanceId}'.");

        return starter.CreateCheckStatusResponse(req, instanceId);
    }
}

And here is the code for the orchestrator function:

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.DurableTask;
using Microsoft.Extensions.Logging;
using SpreadsheetGear;

public static class OrchestratorFunction
{
    [FunctionName("OrchestratorFunction")]
    public static async Task<List<string>> RunOrchestrator(
        [OrchestrationTrigger] IDurableOrchestrationContext context)
    {
        var finalResult = new List<string>();
        return finalResult;
    }
}

This app is configured as “–dotnet-isolated”

Any ideas how this can be fixed?