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.NET Runtime

This reference covers runtime versions, worker configuration, target framework choices, and package dependencies for Azure Functions .NET apps.

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Supported runtimes and models

Model Supported .NET versions Recommended for new apps
Isolated worker .NET 10, .NET 9, .NET 8, .NET Framework 4.8.1 Yes
In-process .NET 8 only No 
flowchart TD
    A[.NET 8 LTS] --> B[Isolated worker]
    C[.NET 9 STS] --> B
    D[In-process] --> E[.NET 8 only]

Required app settings

Setting Value Purpose
FUNCTIONS_WORKER_RUNTIME dotnet-isolated Selects isolated worker runtime
FUNCTIONS_EXTENSION_VERSION ~4 Pins Functions runtime major version
AzureWebJobsStorage connection string or identity-based settings Required host storage 
az functionapp config appsettings set   --name "$APP_NAME"   --resource-group "$RG"   --settings "FUNCTIONS_WORKER_RUNTIME=dotnet-isolated" "FUNCTIONS_EXTENSION_VERSION=~4"
CLI element Explanation
Command(s) az functionapp config appsettings set
Key flags --name, --resource-group, --settings
Variables $APP_NAME, $RG
Expected result Azure CLI applies the configuration change; confirm the returned JSON or follow-up query shows the expected value.

csproj baseline

Use net8.0 as the default target framework for production workloads:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <OutputType>Exe</OutputType>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.*" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.*" OutputItemType="Analyzer" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.*" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="1.*" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Storage" Version="6.*" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Timer" Version="4.*" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.CosmosDB" Version="4.*" />
  </ItemGroup>
</Project>

Build and publish commands

dotnet build
dotnet publish --configuration Release --output ./publish
func azure functionapp publish "$APP_NAME"

Use runtime-safe creation flags when provisioning:

az functionapp create   --name "$APP_NAME"   --resource-group "$RG"   --storage-account "$STORAGE_NAME"   --runtime dotnet-isolated   --runtime-version 8   --functions-version 4   --os-type Linux
CLI element Explanation
Command(s) az functionapp create
Key flags --name, --resource-group, --storage-account, --runtime, --runtime-version, --functions-version, --os-type
Variables $APP_NAME, $RG, $STORAGE_NAME
Expected result Azure CLI returns provisioning details; confirm the resource name and successful provisioning state before continuing.

Upgrade guidance

  1. Move startup logic into Program.cs with HostBuilder.
  2. Replace in-process HTTP abstractions with HttpRequestData and HttpResponseData.
  3. Replace context.GetLogger() with constructor-injected ILogger<T>.
  4. Update trigger attributes and extension packages to isolated-worker equivalents.

See Also

Sources