Migrate apps from Azure Functions version 1.x to version 4.x

This article walks you through the process of safely migrating your function app to run on version 4.x of the Functions runtime. Because project migration instructions are language dependent, make sure to choose your development language from the selector at the top of the article.

If you are running version 1.x of the runtime in Azure Stack Hub, see Considerations for Azure Stack Hub first.

Identify function apps to migrate

Use the following PowerShell script to generate a list of function apps in your subscription that currently target version 1.x:

$Subscription = '<YOUR SUBSCRIPTION ID>' 

Set-AzContext -Subscription $Subscription | Out-Null

$FunctionApps = Get-AzFunctionApp

$AppInfo = @{}

foreach ($App in $FunctionApps)
{
     if ($App.ApplicationSettings["FUNCTIONS_EXTENSION_VERSION"] -like '*1*')
     {
          $AppInfo.Add($App.Name, $App.ApplicationSettings["FUNCTIONS_EXTENSION_VERSION"])
     }
}

$AppInfo

Choose your target .NET version

On version 1.x of the Functions runtime, your C# function app targets .NET Framework.

When you migrate your function app to version 4.x, you have the opportunity to choose the target version of .NET. You can upgrade your C# project to one of the following versions of .NET, all of which can run on Functions version 4.x:

¹ The isolated worker model supports Long Term Support (LTS) and Standard Term Support (STS) versions of .NET, as well as .NET Framework. The in-process model only supports LTS releases of .NET. For a full feature and functionality comparison between the two models, see Differences between in-process and isolate worker process .NET Azure Functions.

This guide doesn't present specific examples for .NET 9. If you need to target that version, you can adapt the .NET 8 examples for the isolated worker model.

Prepare for migration

If you haven't already, identify the list of apps that need to be migrated in your current Azure Subscription by using the Azure PowerShell.

Before you migrate an app to version 4.x of the Functions runtime, you should do the following tasks:

1. Review the list of behavior changes after version 1.x. Migrating from version 1.x to version 4.x also can affect bindings.
2. Complete the steps in Migrate your local project to migrate your local project to version 4.x.
3. After migrating your project, fully test the app locally using version 4.x of the Azure Functions Core Tools.
4. Update your function app in Azure to the new version. If you need to minimize downtime, consider using a staging slot to test and verify your migrated app in Azure on the new runtime version. You can then deploy your app with the updated version settings to the production slot. For more information, see Update using slots.
5. Publish your migrated project to the updated function app.

When you use Visual Studio to publish a version 4.x project to an existing function app at a lower version, you're prompted to let Visual Studio update the function app to version 4.x during deployment. This update uses the same process defined in Update without slots.

Migrate your local project

The following sections describes the updates you must make to your C# project files to be able to run on one of the supported versions of .NET in Functions version 4.x. The updates shown are ones common to most projects. Your project code could require updates not mentioned in this article, especially when using custom NuGet packages.

Migrating a C# function app from version 1.x to version 4.x of the Functions runtime requires you to make changes to your project code. Many of these changes are a result of changes in the C# language and .NET APIs.

Choose the tab that matches your target version of .NET and the desired process model (in-process or isolated worker process).

Project file

The following example is a .csproj project file that runs on version 1.x:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net48</TargetFramework>
    <AzureFunctionsVersion>v1</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="1.0.24" />
  </ItemGroup>
  <ItemGroup>
    <Reference Include="Microsoft.CSharp" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

Use one of the following procedures to update this XML file to run in Functions version 4.x:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <RootNamespace>My.Namespace</RootNamespace>
    <OutputType>Exe</OutputType>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.18.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.13.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
  <ItemGroup>
    <Using Include="System.Threading.ExecutionContext" Alias="ExecutionContext"/>
  </ItemGroup>
</Project>

<OutputType>Exe</OutputType>

<ItemGroup>
<PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.19.0" />
<PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.14.0" />
</ItemGroup>

<ItemGroup>
  <Folder Include="Properties\" />
</ItemGroup>

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net48</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <RootNamespace>My.Namespace</RootNamespace>
    <OutputType>Exe</OutputType>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.18.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.0.13" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.13.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
  <ItemGroup>
    <Folder Include="Properties\" />
  </ItemGroup>
</Project>

  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="4.1.1" />
  </ItemGroup>

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <RootNamespace>My.Namespace</RootNamespace>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="4.1.1" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

Package and namespace changes

Based on the model you are migrating to, you might need to update or change the packages your application references. When you adopt the target packages, you then need to update the namespace of using statements and some types you reference. You can see the effect of these namespace changes on using statements in the HTTP trigger template examples later in this article.

The Notification Hubs and Mobile Apps bindings are supported only in version 1.x of the runtime. When upgrading to version 4.x of the runtime, you need to remove these bindings in favor of working with these services directly using their SDKs.

Program.cs file

In most cases, migrating requires you to add the following program.cs file to your project:

using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureServices(services => {
        services.AddApplicationInsightsTelemetryWorkerService();
        services.ConfigureFunctionsApplicationInsights();
    })
    .Build();

host.Run();

using Microsoft.Extensions.Hosting;
using Microsoft.Azure.Functions.Worker;

namespace Company.FunctionApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
            FunctionsDebugger.Enable();

            var host = new HostBuilder()
                .ConfigureFunctionsWorkerDefaults()
                .ConfigureServices(services => {
                    services.AddApplicationInsightsTelemetryWorkerService();
                    services.ConfigureFunctionsApplicationInsights();
                })
                .Build();
            host.Run();
        }
    }
}

host.json file

Settings in the host.json file apply at the function app level, both locally and in Azure. In version 1.x, your host.json file is either empty or it contains some settings that apply to all functions in the function app. For more information, see Host.json v1. If your host.json file has setting values, review the host.json v2 format for any changes.

To run on version 4.x, you must add "version": "2.0" to the host.json file. You should also consider adding logging to your configuration, as in the following examples:

{
    "version": "2.0",
    "logging": {
        "applicationInsights": {
            "samplingSettings": {
                "isEnabled": true,
                "excludedTypes": "Request"
            },
            "enableLiveMetricsFilters": true
        }
    }
}

{
    "version": "2.0",
    "logging": {
        "applicationInsights": {
            "samplingSettings": {
                "isEnabled": true,
                "excludedTypes": "Request"
            },
            "enableLiveMetricsFilters": true
        }
    }
}

{
    "version": "2.0",
    "logging": {
        "applicationInsights": {
            "samplingSettings": {
                "isEnabled": true,
                "excludedTypes": "Request"
            },
            "enableLiveMetricsFilters": true
        }
    }
}

local.settings.json file

The local.settings.json file is only used when running locally. For information, see Local settings file. In version 1.x, the local.settings.json file has only two required values:

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "AzureWebJobsStorageConnectionStringValue",
        "AzureWebJobsDashboard": "AzureWebJobsStorageConnectionStringValue"
    }
}

When you migrate to version 4.x, make sure that your local.settings.json file has at least the following elements:

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

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

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "AzureWebJobsStorageConnectionStringValue",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet",
        "FUNCTIONS_INPROC_NET8_ENABLED": "1"
    }
}

Class name changes

Some key classes changed names between version 1.x and version 4.x. These changes are a result either of changes in .NET APIs or in differences between in-process and isolated worker process. The following table indicates key .NET classes used by Functions that could change when migrating:

There might also be class name differences in bindings. For more information, see the reference articles for the specific bindings.

Other code changes

HTTP trigger template

Most of the code changes between version 1.x and version 4.x can be seen in HTTP triggered functions. The HTTP trigger template for version 1.x looks like the following example:

using System.Linq;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.Host;

namespace Company.Function
{
    public static class HttpTriggerCSharp
    {
        [FunctionName("HttpTriggerCSharp")]
        public static async Task<HttpResponseMessage> 
            Run([HttpTrigger(AuthorizationLevel.AuthLevelValue, "get", "post", 
            Route = null)]HttpRequestMessage req, TraceWriter log)
        {
            log.Info("C# HTTP trigger function processed a request.");

            // parse query parameter
            string name = req.GetQueryNameValuePairs()
                .FirstOrDefault(q => string.Compare(q.Key, "name", true) == 0)
                .Value;

            if (name == null)
            {
                // Get request body
                dynamic data = await req.Content.ReadAsAsync<object>();
                name = data?.name;
            }

            return name == null
                ? req.CreateResponse(HttpStatusCode.BadRequest, 
                    "Please pass a name on the query string or in the request body")
                : req.CreateResponse(HttpStatusCode.OK, "Hello " + name);
        }
    }
}

In version 4.x, the HTTP trigger template looks like the following example:

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;

namespace Company.Function
{
    public class HttpTriggerCSharp
    {
        private readonly ILogger<HttpTriggerCSharp> _logger;

        public HttpTriggerCSharp(ILogger<HttpTriggerCSharp> logger)
        {
            _logger = logger;
        }

        [Function("HttpTriggerCSharp")]
        public IActionResult Run(
            [HttpTrigger(AuthorizationLevel.Function, "get")] HttpRequest req)
        {
            _logger.LogInformation("C# HTTP trigger function processed a request.");

            return new OkObjectResult($"Welcome to Azure Functions, {req.Query["name"]}!");
        }
    }
}

using Microsoft.Azure.Functions.Worker;
using Microsoft.Azure.Functions.Worker.Http;
using Microsoft.Extensions.Logging;
using System.Net;

namespace Company.Function
{
    public class HttpTriggerCSharp
    {
        private readonly ILogger<HttpTriggerCSharp> _logger;

        public HttpTriggerCSharp(ILogger<HttpTriggerCSharp> logger)
        {
            _logger = logger;
        }

        [Function("HttpTriggerCSharp")]
        public HttpResponseData Run([HttpTrigger(AuthorizationLevel.Function, "get")] HttpRequestData req)
        {
            _logger.LogInformation("C# HTTP trigger function processed a request.");

            var response = req.CreateResponse(HttpStatusCode.OK);
            response.Headers.Add("Content-Type", "text/plain; charset=utf-8");

            response.WriteString($"Welcome to Azure Functions, {req.Query["name"]}!");

            return response;
        }
    }
}

using System;
using System.IO;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;

namespace Company.Function
{
    public static class HttpTriggerCSharp
    {
        [FunctionName("HttpTriggerCSharp")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.AuthLevelValue, "get", "post", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            string name = req.Query["name"];

            string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
            dynamic data = JsonConvert.DeserializeObject(requestBody);
            name = name ?? data?.name;

            string responseMessage = string.IsNullOrEmpty(name)
                ? "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response."
                : $"Hello, {name}. This HTTP triggered function executed successfully.";

            return new OkObjectResult(responseMessage);
        }
    }
}

To update your project to Azure Functions 4.x:

1. Update your local installation of Azure Functions Core Tools to version 4.x.

2. Move to one of the Node.js versions supported on version 4.x.

3. Add both version and extensionBundle elements to the host.json, so that it looks like the following example:

   {
       "version": "2.0",
       "extensionBundle": {
           "id": "Microsoft.Azure.Functions.ExtensionBundle",
           "version": "[3.3.0, 4.0.0)"
       }
   }
   

   The extensionBundle element is required because after version 1.x, bindings are maintained as external packages. For more information, see Extension bundles.

4. Update your local.settings.json file so that it has at least the following elements:

   {
       "IsEncrypted": false,
       "Values": {
           "AzureWebJobsStorage": "UseDevelopmentStorage=true",
           "FUNCTIONS_WORKER_RUNTIME": "node"
       }
   }
   

   The AzureWebJobsStorage setting can be either the Azurite storage emulator or an actual Azure storage account. For more information, see Local storage emulator.

Upgrade your function app in Azure

You need to upgrade the runtime of the function app host in Azure to version 4.x before you publish your migrated project. The runtime version used by the Functions host is controlled by the FUNCTIONS_EXTENSION_VERSION application setting, but in some cases other settings must also be updated. Both code changes and changes to application settings require your function app to restart.

The easiest way is to upgrade without slots and then republish your app project. You can also minimize the downtime in your app and simplify rollback by upgrading using slots.

Upgrade without slots

The simplest way to upgrade to v4.x is to set the FUNCTIONS_EXTENSION_VERSION application setting to ~4 on your function app in Azure. You must follow a different procedure on a site with slots.

az functionapp config appsettings set --settings FUNCTIONS_EXTENSION_VERSION=~4 -g <RESOURCE_GROUP_NAME> -n <APP_NAME>

Update-AzFunctionAppSetting -AppSetting @{"FUNCTIONS_EXTENSION_VERSION" = "~4"} -Name <APP_NAME> -ResourceGroupName <RESOURCE_GROUP_NAME> -Force

During upgrade, you must also set another setting, which differs between Windows and Linux.

az functionapp config set --net-framework-version v6.0 -g <RESOURCE_GROUP_NAME> -n <APP_NAME>

Set-AzWebApp -NetFrameworkVersion v6.0 -Name <APP_NAME> -ResourceGroupName <RESOURCE_GROUP_NAME>

az functionapp config set --name <APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --linux-fx-version "DOTNET|6.0"

az functionapp config set --name <APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --linux-fx-version "Java|11"

az functionapp config set --name <APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --linux-fx-version "Node|16"

az functionapp config set --name <APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --linux-fx-version "Python|3.9"

In this example, replace <APP_NAME> with the name of your function app and <RESOURCE_GROUP_NAME> with the name of the resource group.

You can now republish your app project that has been migrated to run on version 4.x.

Upgrade using slots

Using deployment slots is a good way to upgrade your function app to the v4.x runtime from a previous version. By using a staging slot, you can run your app on the new runtime version in the staging slot and switch to production after verification. Slots also provide a way to minimize downtime during upgrade. If you need to minimize downtime, follow the steps in Minimum downtime upgrade.

After you've verified your app in the upgraded slot, you can swap the app and new version settings into production. This swap requires setting WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 in the production slot. How you add this setting affects the amount of downtime required for the upgrade.

Standard upgrade

If your slot-enabled function app can handle the downtime of a full restart, you can update the WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS setting directly in the production slot. Because changing this setting directly in the production slot causes a restart that impacts availability, consider doing this change at a time of reduced traffic. You can then swap in the upgraded version from the staging slot.

The Update-AzFunctionAppSetting PowerShell cmdlet doesn't currently support slots. You must use Azure CLI or the Azure portal.

1. Use the following command to set WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 in the production slot:

   az functionapp config appsettings set --settings WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0  -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> 
   

   In this example, replace <APP_NAME> with the name of your function app and <RESOURCE_GROUP_NAME> with the name of the resource group. This command causes the app running in the production slot to restart.

2. Use the following command to also set WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS in the staging slot:

   az functionapp config appsettings set --settings WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME>
   

3. Use the following command to change FUNCTIONS_EXTENSION_VERSION and upgrade the staging slot to the new runtime version:

   az functionapp config appsettings set --settings FUNCTIONS_EXTENSION_VERSION=~4 -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME>
   

4. Version 4.x of the Functions runtime requires .NET 6 in Windows. On Linux, .NET apps must also upgrade to .NET 6. Use the following command so that the runtime can run on .NET 6:

   • Windows
   • Linux

   When running on Windows, you also need to enable .NET 6.0, which is required by version 4.x of the runtime.

   az functionapp config set --net-framework-version v6.0 -g <RESOURCE_GROUP_NAME> -n <APP_NAME>
   

   .NET 6 is required for function apps in any language running on Windows.

   In this example, replace <APP_NAME> with the name of your function app and <RESOURCE_GROUP_NAME> with the name of the resource group.

5. If your code project required any updates to run on version 4.x, deploy those updates to the staging slot now.

6. Confirm that your function app runs correctly in the upgraded staging environment before swapping.

7. Use the following command to swap the upgraded staging slot to production:

   az functionapp deployment slot swap -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME> --target-slot production
   

Minimum downtime upgrade

To minimize the downtime in your production app, you can swap the WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS setting from the staging slot into production. After that, you can swap in the upgraded version from a prewarmed staging slot.

1. Use the following command to set WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 in the staging slot:

   az functionapp config appsettings set --settings WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME>
   

2. Use the following commands to swap the slot with the new setting into production, and at the same time restore the version setting in the staging slot.

   az functionapp deployment slot swap -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME> --target-slot production
   az functionapp config appsettings set --settings FUNCTIONS_EXTENSION_VERSION=~3 -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME>
   

   You may see errors from the staging slot during the time between the swap and the runtime version being restored on staging. This error can happen because having WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 only in staging during a swap removes the FUNCTIONS_EXTENSION_VERSION setting in staging. Without the version setting, your slot is in a bad state. Updating the version in the staging slot right after the swap should put the slot back into a good state, and you call roll back your changes if needed. However, any rollback of the swap also requires you to directly remove WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 from production before the swap back to prevent the same errors in production seen in staging. This change in the production setting would then cause a restart.

3. Use the following command to again set WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 in the staging slot:

   az functionapp config appsettings set --settings WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME>
   

   At this point, both slots have WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS=0 set.

4. Use the following command to change FUNCTIONS_EXTENSION_VERSION and upgrade the staging slot to the new runtime version:

   az functionapp config appsettings set --settings FUNCTIONS_EXTENSION_VERSION=~4 -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME>
   

5. Version 4.x of the Functions runtime requires .NET 6 in Windows. On Linux, .NET apps must also upgrade to .NET 6. Use the following command so that the runtime can run on .NET 6:

   • Windows
   • Linux

   When running on Windows, you also need to enable .NET 6.0, which is required by version 4.x of the runtime.

   az functionapp config set --net-framework-version v6.0 -g <RESOURCE_GROUP_NAME> -n <APP_NAME>
   

   .NET 6 is required for function apps in any language running on Windows.

   In this example, replace <APP_NAME> with the name of your function app and <RESOURCE_GROUP_NAME> with the name of the resource group.

6. If your code project required any updates to run on version 4.x, deploy those updates to the staging slot now.

7. Confirm that your function app runs correctly in the upgraded staging environment before swapping.

8. Use the following command to swap the upgraded and prewarmed staging slot to production:

   az functionapp deployment slot swap -g <RESOURCE_GROUP_NAME>  -n <APP_NAME> --slot <SLOT_NAME> --target-slot production