'Error "Did not find functions with language [dotnet-isolated]" in Azure Function when migrating from .NET 3 to .NET 5

I'm trying to migrate an Azure Function that works perfectly on .NET 3.1 to .NET 5. I followed Microsoft's GitHub guide and still can't get it to run or debug locally (didn't even try to publish to Azure).

I'm getting this error:

[2021-09-05T09:49:33.066Z] A host error has occurred during startup operation 'bb37a6db-b6f4-4396-bb9b-cb5ae0bba387'.
[2021-09-05T09:49:33.067Z] Microsoft.Azure.WebJobs.Script: Did not find functions with language [dotnet-isolated].

And this exception is being raised:

This is my Program.cs:

static async Task Main(string[] args)
        {
            var host = new HostBuilder()
               .ConfigureAppConfiguration(c =>
               {
                   c.AddCommandLine(args);
               })
               .ConfigureServices(s =>
               {
                   s.AddLogging();
               })
               .Build();

            await host.RunAsync();
        }

This is my project file:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net5.0</TargetFramework>
    <AzureFunctionsVersion>v3</AzureFunctionsVersion>
    <UserSecretsId>76d0a5ed-221b-4b35-8ff4-3ee33d393196</UserSecretsId>
    <OutputType>Exe</OutputType>
    <_FunctionsSkipCleanOutput>true</_FunctionsSkipCleanOutput>
  </PropertyGroup>
  <ItemGroup>
    <None Remove="global.json" />
  </ItemGroup>
  <ItemGroup>
    <Content Include="global.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <ExcludeFromSingleFile>true</ExcludeFromSingleFile>
      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
    </Content>
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.5.1" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Storage" Version="4.0.4" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.0.4" />
    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="5.0.2" />
    <PackageReference Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.11.1" />
    <PackageReference Include="System.Linq.Async" Version="5.0.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="config.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

My local.settings.json:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "HIDDEN",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated"
  }
}

My host.json:

{
  "logging": {
    "fileLoggingMode": "always",
    "logLevel": {
      //"QueueWorkers.EmailQueueWorker": "Trace",
      //"QueueWorkers.EmailQueueWorker.EmailQueueWorker": "Trace",
      "default": "Information",
      "Function": "Trace",
      "Host.Results": "Error",
      "Host.Aggregator": "Trace"
    },
    "applicationInsights": {
      //"samplingExcludedTypes": "Request",
      "samplingSettings": {
        "isEnabled": true
      }
    },
    "console": {
      "isEnabled": "true"
    }
  },
  "Values": {
    "AzureWebJobsStorage": "HIDDEN",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated"
  },
  "extensions": {
    "queues": {
      "maxDequeueCount": 5,
      "maxPollingInterval": "00:00:02"
    }
  },
  "version": "2.0"
}

Thanks

c++sharpazure.net-coreazure-functions


Solution 1:[1]

Had a similar problem in Visual Studio 2022, while trying to migrate a project from .net 5 to .net 6 functions...

kept telling me "Microsoft.Azure.WebJobs.Script: Did not find functions with language [dotnet-isolated]"

enter image description here

My Solution

1) I was missing: Program.cs

using Microsoft.Azure.Functions.Worker.Configuration;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using System.Threading.Tasks;

namespace Main.Function
{
    public class Program
    {
        public static void Main()
        {
            var host = new HostBuilder()
                .ConfigureFunctionsWorkerDefaults()
                .Build();

            host.Run();
        }
    }
}

2) Edit .csproj > Under ItemGroup...

Remove:

<PackageReference Include="Microsoft.NET.Sdk.Functions" Version="4.0.1" />

Replace with

<PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.0.13" />
      <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.3.0" OutputItemType="Analyzer" />
      <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.6.0" />
      <PackageReference Include="Microsoft.Azure.WebJobs.Script.ExtensionsMetadataGenerator" Version="4.0.1" />

3) Ensure OutputType is set to exe

<OutputType>Exe</OutputType>

enter image description here

4) Unload project and reload (delete bin and obj folder before building)

Solution 2:[2]

In Azure navigate to your Function and then change the settings:

"FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated"

enter image description here

Solution 3:[3]

Well, still couldn't directly launch and debug from VS 2019 but function does work if launched from CLI and debug is working.

  1. Add Debugger.Launch(); to Program.cs (first line of Main method)
  2. Make sure you have <LangVersion>preview</LangVersion> in your csproj (right after TargetFramework). This missing line was actually the critical difference that stopped my function from working.
  3. Launch from CLI (from function folder): "func start --verbose"

Thanks

Solution 4:[4]

"FUNCTIONS_WORKER_RUNTIME": "dotnet"

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Dwain Browne
Solution 2 Liam
Solution 3
Solution 4 Romesh

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