Migrates Azure Functions projects from in-process Startup hooks (FunctionsStartup, IFunctionsHostBuilder) to the isolated worker model with Program.cs service registration. Use when upgrading Azure Functions from in-process to isolated, migrating Startup.cs to Program.cs, removing Microsoft.Azure.Functions.Extensions, or converting FunctionsHostBuilderContext to HostBuilderContext. Triggers for Startup.cs, FunctionsStartup, ConfigureFunctionsWorkerDefaults, ConfigureFunctionsWebApplication, and project files (.csproj, .vbproj, .fsproj) referencing Microsoft.NET.Sdk.Functions.
Instrucciones de origen · Vista previa de solo lectura
name
migrating-azure-functions-startup
description
Migrates Azure Functions projects from in-process Startup hooks (FunctionsStartup, IFunctionsHostBuilder) to the isolated worker model with Program.cs service registration. Use when upgrading Azure Functions from in-process to isolated, migrating Startup.cs to Program.cs, removing Microsoft.Azure.Functions.Extensions, or converting FunctionsHostBuilderContext to HostBuilderContext. Triggers for Startup.cs, FunctionsStartup, ConfigureFunctionsWorkerDefaults, ConfigureFunctionsWebApplication, and project files (.csproj, .vbproj, .fsproj) referencing Microsoft.NET.Sdk.Functions.
Migrate Azure Functions from the in-process model (using FunctionsStartup and IFunctionsHostBuilder) to the isolated worker model, moving all service registrations and configuration from Startup.cs into Program.cs.
Related skill: For upgrading an already-isolated project to the V2 hosting pattern (IHostApplicationBuilder), use migrating-azure-functions-to-v2 instead.
The startup file may not be named Startup.cs.Identify it by looking for classes inheriting FunctionsStartup, usage of IFunctionsHostBuilder or FunctionsHostBuilderContext, or the [assembly: FunctionsStartup(...)] attribute. Throughout this skill, "Startup.cs" refers to whichever file contains these patterns.
Additional signals: in-process uses [FunctionName] attribute; isolated has Program.cs with a host builder.
Step 3: Determine Upgrade Path
Already isolated → skip to Phase 2.
.NET 8 in-process → ask user whether to also upgrade the framework, or just switch to isolated model.
.NET 6 in-process → upgrade to .NET 8+ using isolated worker model (start .NET upgrade scenario flow).
Step 4: Check ASP.NET Core Integration
Determine whether the project uses ASP.NET Core integration. This controls the builder method in Program.cs:
With ASP.NET Core → ConfigureFunctionsWebApplication()
Without → ConfigureFunctionsWorkerDefaults()
Phase 2: Execution
Step 1: Remove Obsolete Packages
Remove Microsoft.Azure.Functions.Extensions from the project file. This package only supports in-process and causes build conflicts with the isolated model.
Step 2: Comment Out Startup.cs
Comment out the entire class rather than deleting the file — this preserves the original code as a rollback reference until the user verifies the migration works.
// Logic has been moved to Program.cs. Delete this file once migration is verified./*
[assembly: FunctionsStartup(typeof(MyNamespace.Startup))]
namespace MyNamespace
{
public class Startup : FunctionsStartup
{
public override void Configure(IFunctionsHostBuilder builder)
{
builder.Services.AddSingleton<IMyService, MyService>();
}
}
}
*/
Step 3: Create or Update Program.cs
Use the appropriate builder method based on Step 4 above.
Without ASP.NET Core integration:
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
var host = new HostBuilder()
.ConfigureFunctionsWorkerDefaults()
.ConfigureServices((context, services) =>
{
// Migrated from Startup.cs
})
.Build();
host.Run();
With ASP.NET Core integration:
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
var host = new HostBuilder()
.ConfigureFunctionsWebApplication()
.ConfigureServices((context, services) =>
{
// Migrated from Startup.cs
})
.Build();
host.Run();
Step 4: Migrate Service Registrations
Move all registrations from IFunctionsHostBuilder.Services into the ConfigureServices lambda.
If FunctionsHostBuilderContext was used, replace with HostBuilderContext and add a comment explaining the scope change — in the in-process model, custom configuration could influence the host; in isolated mode it applies to the worker only.
Before (Startup.cs):
publicoverridevoidConfigure(IFunctionsHostBuilder builder)
{
var context = builder.GetContext();
var connectionString = context.Configuration["ConnectionStrings:MyDb"];
builder.Services.AddSingleton<IMyService, MyService>();
builder.Services.AddDbContext<MyDbContext>(options =>
options.UseSqlServer(connectionString));
}
After (Program.cs):
.ConfigureServices((context, services) =>
{
// Note: Custom configuration sources now apply to worker only (not host).var connectionString = context.Configuration["ConnectionStrings:MyDb"];
services.AddSingleton<IMyService, MyService>();
services.AddDbContext<MyDbContext>(options =>
options.UseSqlServer(connectionString));
})
Step 5: Handle Build Failures
If build errors persist after migration, add a placeholder to signal incomplete migration and notify the user that manual review is required:
.ConfigureServices((context, services) =>
{
thrownew NotImplementedException(
"Migrate services from Startup.cs to ConfigureServices within Program.cs.");
})
Step 6: Verify
Confirm:
Isolated worker packages are referenced; no in-process packages remain
Microsoft.Azure.Functions.Extensions is removed
Startup.cs is commented out with a deletion note
Program.cs uses the correct builder method
All service registrations and configuration are migrated
Project builds without errors
Notify the user to review the migration, test all functions, and delete Startup.cs once verified.
Success Criteria
Project uses isolated worker model (Microsoft.Azure.Functions.Worker packages)
No in-process packages remain (Microsoft.NET.Sdk.Functions, Microsoft.Azure.WebJobs.*)
Microsoft.Azure.Functions.Extensions removed
Startup.cs commented out (not deleted) with migration note
Program.cs uses correct builder method
All service registrations migrated; FunctionsHostBuilderContext replaced with HostBuilderContext
