Migrating Durable Functions to .NET 8 Isolated

Anthony Giretti documents the migration of Azure Durable Functions from .NET 6 in-process to .NET 8 isolated, based on a real migration project. Non-Durable Functions moved easily; Durable Functions did not, and the post walks through every API that changed shape: the project file, the NuGet packages, and the four building blocks of the Durable Functions programming model (activities, entities, orchestrators, clients).

The core pattern across all four blocks is the same: WebJobs-namespaced packages and interfaces (IDurableOrchestrationContext, IDurableEntityContext, IDurableOrchestrationClient) give way to Worker-namespaced replacements (TaskOrchestrationContext, TaskEntityDispatcher, DurableTaskClient), and the generic GetInput<T>() call disappears in favor of typing the input directly as a function parameter.

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• The .csproj needs TargetFramework set to net8.0, AzureFunctionsVersion to v4, and OutputType to Exe for isolated mode to run at all.
• A “Function already exists” crash is fixed by adding <FunctionsEnableWorkerIndexing>False</FunctionsEnableWorkerIndexing> to the csproj.
• Every NuGet package under Microsoft.Azure.WebJobs.* gets replaced by its Microsoft.Azure.Functions.Worker.* equivalent; Microsoft.Azure.Functions.Worker.Sdk, .Extensions, and .Worker itself are required additions for isolated mode.
• local.settings.json needs FUNCTIONS_WORKER_RUNTIME changed from dotnet to dotnet-isolated.
• Startup.cs is replaced by a Program.cs built around HostBuilder, with Application Insights wired through AddApplicationInsightsTelemetryWorkerService() and ConfigureFunctionsApplicationInsights(); a specific logging-rule removal is needed at the end of the chain to avoid a known custom-logging issue (linked to an open Azure SDK GitHub issue).
• Activity functions: [FunctionName] becomes [Function], IDurableActivityContext and its GetInput<T>() call disappear, and the typed input becomes the method parameter directly. An activity with no input takes a FunctionContext parameter instead.
• Entity functions: IDurableEntityContext is replaced by TaskEntityDispatcher, keeping the same DispatchAsync<T>() call.
• Orchestrator functions see the widest set of changes: IDurableOrchestrationContext becomes TaskOrchestrationContext; context.LockAsync() becomes await using (await context.Entities.LockEntitiesAsync()); CallActivityWithRetryAsync is replaced by a single CallActivityAsync overload that takes retry options via TaskOptions.FromRetryPolicy(new RetryPolicy(...)), with parameters and options in reversed order from the old signature; and context.SetOutput() is gone, replaced by changing the method’s return type to Task<string> and returning the value directly.
• Durable clients: IDurableOrchestrationClient becomes DurableTaskClient, and StartNewAsync() becomes ScheduleNewOrchestrationInstanceAsync().