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gewarren merged 7 commits into from
Jan 28, 2026
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Add more uses of AnyKey #51322

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add more uses of AnyKey
gewarren Jan 27, 2026
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Update docs/core/extensions/dependency-injection/overview.md
gewarren Jan 27, 2026
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gewarren Jan 27, 2026
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Merge branch 'anykey2' of github.com:gewarren/docs into anykey2
gewarren Jan 27, 2026
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actually save file first
gewarren Jan 27, 2026
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use correct snippet tag
gewarren Jan 27, 2026
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Update docs/core/extensions/dependency-injection/overview.md
gewarren Jan 28, 2026
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20 changes: 14 additions & 6 deletions docs/core/compatibility/extensions/10.0/getkeyedservice-anykey.md
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@@ -1,13 +1,16 @@
---
title: "Breaking change: Fix issues in GetKeyedService() and GetKeyedServices() with AnyKey"
description: "Learn about the breaking change in .NET 10 where GetKeyedService() and GetKeyedServices() behavior changed when using KeyedService.AnyKey as the lookup key."
ms.date: 11/19/2025
ms.date: 01/26/2026
ai-usage: ai-assisted
---

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

The behavior of the <xref:Microsoft.Extensions.DependencyInjection.ServiceProviderKeyedServiceExtensions.GetKeyedService(System.IServiceProvider,System.Type,System.Object)> and <xref:Microsoft.Extensions.DependencyInjection.ServiceProviderKeyedServiceExtensions.GetKeyedServices(System.IServiceProvider,System.Type,System.Object)> methods in the `Microsoft.Extensions.DependencyInjection` library was updated to address inconsistencies in handling the <xref:Microsoft.Extensions.DependencyInjection.KeyedService.AnyKey?displayProperty=nameWithType> registration. Specifically, `GetKeyedService()` now throws an exception when you attempt to resolve a single service using `KeyedService.AnyKey` as the lookup key, and `GetKeyedServices()` (plural) no longer returns `AnyKey` registrations when queried with `KeyedService.AnyKey`.
The behavior of the <xref:Microsoft.Extensions.DependencyInjection.ServiceProviderKeyedServiceExtensions.GetKeyedService(System.IServiceProvider,System.Type,System.Object)> and <xref:Microsoft.Extensions.DependencyInjection.ServiceProviderKeyedServiceExtensions.GetKeyedServices(System.IServiceProvider,System.Type,System.Object)> methods in the `Microsoft.Extensions.DependencyInjection` library was updated to address inconsistencies in handling the <xref:Microsoft.Extensions.DependencyInjection.KeyedService.AnyKey?displayProperty=nameWithType> registration. Specifically:

- `GetKeyedService()` now throws an exception when you attempt to resolve a single service using `KeyedService.AnyKey` as the lookup key.
- `GetKeyedServices()` (plural) no longer returns `AnyKey` registrations when queried with `KeyedService.AnyKey`.

## Version introduced

Expand All @@ -32,7 +35,7 @@ Additionally, calling `GetKeyedServices()` with `KeyedService.AnyKey` no longer

```csharp
var services = serviceProvider.GetKeyedServices(typeof(IMyService), KeyedService.AnyKey);
// Returns an empty collection.
// Returns only services that were registered with a specific key.
```

## Type of breaking change
Expand All @@ -41,14 +44,19 @@ This change is a [behavioral change](../../categories.md#behavioral-change).

## Reason for change

The previous behavior of `GetKeyedService()` and `GetKeyedServices()` with `KeyedService.AnyKey` was inconsistent with the intended semantics of `AnyKey`. The changes were introduced to ensure that `AnyKey` is treated as a special case and can't be used to resolve a single service, and to prevent `GetKeyedServices()` from returning `AnyKey` registrations when queried with `AnyKey`. These updates improve the predictability and correctness of the `Microsoft.Extensions.DependencyInjection` library's behavior when working with keyed services. For more details, see the [pull request](https://github.com/dotnet/runtime/pull/113137) and the associated [merge commit](https://github.com/dotnet/runtime/commit/deee462fc8421a7e18b8916eb5a5eacb9d09169d).
The previous behavior of `GetKeyedService()` and `GetKeyedServices()` with `KeyedService.AnyKey` was inconsistent with the intended semantics of `AnyKey`. The changes were introduced to:

- Ensure that `AnyKey` is treated as a special case and can't be used to resolve a single service.
- Prevent `GetKeyedServices()` from returning `AnyKey` registrations when queried with `AnyKey`.

These updates improve the predictability and correctness of the `Microsoft.Extensions.DependencyInjection` library's behavior when working with keyed services. For more details, see the [pull request](https://github.com/dotnet/runtime/pull/113137) and the associated [merge commit](https://github.com/dotnet/runtime/commit/deee462fc8421a7e18b8916eb5a5eacb9d09169d).

## Recommended action

If you use `GetKeyedService()` or `GetKeyedServices()` with `KeyedService.AnyKey`, review your code and update it to use specific keys instead of `AnyKey`:

- Replace `GetKeyedService(KeyedService.AnyKey)` calls with specific keys or alternative logic to handle service resolution.
- Replace `GetKeyedServices(KeyedService.AnyKey)` calls with specific keys, or update your logic to enumerate only the services you intend to retrieve.
- Update `GetKeyedService(KeyedService.AnyKey)` calls to pass specific keys, or use alternative logic to handle service resolution.
- Update `GetKeyedServices(KeyedService.AnyKey)` calls to pass specific keys, or use alternative logic to enumerate only the services you intend to retrieve.

## Affected APIs

Expand Down
18 changes: 15 additions & 3 deletions docs/core/extensions/dependency-injection/overview.md
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---
title: Dependency injection
description: Learn how to use dependency injection within your .NET apps. Discover how to define service lifetimes and express dependencies in C#.
ms.date: 10/21/2025
ms.date: 01/26/2026
ms.topic: overview
ai-usage: ai-assisted
---
Expand Down Expand Up @@ -216,7 +216,11 @@ public class ExampleService

### KeyedService.AnyKey property

The <xref:Microsoft.Extensions.DependencyInjection.KeyedService.AnyKey?displayProperty=nameWithType> property provides a special key for working with keyed services. You can register a service using `KeyedService.AnyKey` as a fallback that matches any key. This is useful when you want to provide a default implementation for any key that doesn't have an explicit registration.
The <xref:Microsoft.Extensions.DependencyInjection.KeyedService.AnyKey?displayProperty=nameWithType> property provides a special key for working with keyed services.

#### Service registration

You can register a service using `KeyedService.AnyKey` as a fallback that matches any key. This is useful when you want to provide a default implementation for any key that doesn't have an explicit registration.

:::code language="csharp" source="snippets/anykey/Program.cs" id="FallbackRegistration":::

Expand All @@ -225,8 +229,16 @@ In the preceding example:
- Requesting `ICache` with key `"premium"` returns the `PremiumCache` instance.
- Requesting `ICache` with any other key (like `"basic"` or `"standard"`) creates a new `DefaultCache` using the `AnyKey` fallback.

#### Query for services

You can query for all services that were registered *using a specific key* (that is, not with `KeyedService.AnyKey`), by passing `KeyedService.AnyKey` to <xref:Microsoft.Extensions.DependencyInjection.ServiceProviderKeyedServiceExtensions.GetKeyedServices``1(System.IServiceProvider,System.Object)>.

:::code language="csharp" source="snippets/anykey/Program.cs" id="AnyKeyQuery":::

In the preceding example, calling `GetKeyedServices<T>(KeyedService.AnyKey)` returns only the `PremiumCache` instance since it's the only cache that was registered using a specific key in the [service registration](#service-registration) code example.

> [!IMPORTANT]
> Starting in .NET 10, calling `GetKeyedService()` with `KeyedService.AnyKey` throws an <xref:System.InvalidOperationException> because `AnyKey` is intended as a registration fallback, not as a query key. For more information, see [Fix issues in GetKeyedService() and GetKeyedServices() with AnyKey](../../compatibility/extensions/10.0/getkeyedservice-anykey.md).
> Starting in .NET 10, calling `GetKeyedService()` (singular) with `KeyedService.AnyKey` throws an <xref:System.InvalidOperationException> because `AnyKey` shouldn't be used to resolve a single service. For more information, see [Fix issues in GetKeyedService() and GetKeyedServices() with AnyKey](../../compatibility/extensions/10.0/getkeyedservice-anykey.md).

## See also

Expand Down
28 changes: 24 additions & 4 deletions docs/core/extensions/dependency-injection/snippets/anykey/Program.cs
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Expand Up @@ -17,17 +17,37 @@ static void FallbackExample()
// Register a specific cache for the "premium" key.
services.AddKeyedSingleton<ICache>("premium", new PremiumCache());

var provider = services.BuildServiceProvider();
ServiceProvider provider = services.BuildServiceProvider();

// Requesting with "premium" key returns PremiumCache.
var premiumCache = provider.GetKeyedService<ICache>("premium");
ICache? premiumCache = provider.GetKeyedService<ICache>("premium");
Console.WriteLine($"Premium key: {premiumCache}");

// Requesting with any other key uses the AnyKey fallback.
var basicCache = provider.GetKeyedService<ICache>("basic");
ICache? basicCache = provider.GetKeyedService<ICache>("basic");
Console.WriteLine($"Basic key: {basicCache}");

var standardCache = provider.GetKeyedService<ICache>("standard");
ICache? standardCache = provider.GetKeyedService<ICache>("standard");
Console.WriteLine($"Standard key: {standardCache}");

/* This example outputs:
*
* Premium key: Premium cache
* Basic key: basic cache
* Standard key: standard cache
*/
// </FallbackRegistration>

// <AnyKeyQuery>
IEnumerable<ICache>? keyedCaches = provider.GetKeyedServices<ICache>(KeyedService.AnyKey);
foreach (ICache cache in keyedCaches)
{
Console.WriteLine($"AnyKey registered cache: {cache}");
}

/* This example outputs:
*
* AnyKey registered cache: Premium cache
*/
// </AnyKeyQuery>
}