manus-skills/.kortix/opencode/skills/coding/migrate-dotnet9-to-dotnet10/references/extensions-hosting-dotnet9to10.md

Extensions and Hosting Breaking Changes (.NET 10)

These changes affect projects using Microsoft.Extensions.Hosting, BackgroundService, Microsoft.Extensions.Configuration, and related libraries.

Behavioral Changes

BackgroundService.ExecuteAsync runs entirely on a background thread

Impact: Medium. Previously, the synchronous code in ExecuteAsync before the first await ran on the main thread during startup, blocking other hosted services from starting. Now ALL of ExecuteAsync runs on a background thread.

If startup ordering matters:

// Option 1: Move synchronous startup code to StartAsync
public override async Task StartAsync(CancellationToken cancellationToken)
{
    // This still runs synchronously during startup
    InitializeResources();
    await base.StartAsync(cancellationToken);
}

// Option 2: Use IHostedLifecycleService for fine-grained lifecycle control
public class MyService : BackgroundService, IHostedLifecycleService
{
    public Task StartingAsync(CancellationToken ct)
    {
        // runs before StartAsync
        return Task.CompletedTask;
    }

    public Task StartedAsync(CancellationToken ct)
    {
        // runs after StartAsync
        return Task.CompletedTask;
    }
    // ... other lifecycle methods
}

// Option 3: Move code to the constructor
public MyService(ILogger<MyService> logger)
{
    // Constructor code runs during DI resolution
}

Null values preserved in configuration

Impact: Medium. JSON null values are now properly bound instead of being converted to empty strings or ignored. Empty arrays ([]) are also now correctly bound as empty arrays instead of being ignored.

Scenario	.NET 9 behavior	.NET 10 behavior
"StringProperty": null	Bound as "" (empty string)	Bound as null (overwrites constructor default)
"IntProperty": null	Ignored (kept constructor default)	Bound as null (if int?)
"Array": [null, null]	Bound as ["", ""]	Bound as [null, null]
"Array": []	Ignored (null)	Bound as empty array []

If you need the old behavior:

• Replace null with "" in JSON config files
• Or remove null entries to skip binding

Fix issues in GetKeyedService() and GetKeyedServices() with AnyKey

GetKeyedService() and GetKeyedServices() with AnyKey now work correctly. If your code relied on the previous buggy behavior, update it.

Message no longer duplicated in Console log output

When using the JSON console logger, messages are no longer duplicated. If your log parsing relied on the duplicated format, update it.

ProviderAliasAttribute moved to Microsoft.Extensions.Logging.Abstractions assembly

ProviderAliasAttribute has moved assemblies. If you reference it directly by assembly-qualified name, update the reference. Source-incompatible for code using assembly-qualified type references.

Removed DynamicallyAccessedMembers annotation from trim-unsafe configuration code

The [DynamicallyAccessedMembers] annotation was removed from certain configuration APIs that are not trim-safe. Binary incompatible for code that relied on the annotation for trimming analysis.