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Home Interviews What is AddKeyedTransient? – MindStick
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2 Answers

Yogendra Mohan
Yogendra Mohan 14 Aug 2026
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AddKeyedTransient lets you register multiple implementations of the same interface using different keys, with a Transient lifetime.

services.AddKeyedTransient<IPayment, StripePayment>("stripe");
services.AddKeyedTransient<IPayment, RazorpayPayment>("razorpay");

Then you can request one by its key:

[FromKeyedServices("stripe")] IPayment payment

In simple words:

Same interface + different implementations + choose using a key.

Anubhav Sharma
Anubhav Sharma 04 Aug 2026
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AddKeyedTransient is a dependency injection (DI) registration method in ASP.NET Core that lets you register multiple implementations of the same service type, each identified by a key. It was introduced in .NET 8 as part of the new keyed services feature.

Unlike AddTransient, which registers a single implementation (or multiple without an easy way to distinguish them), AddKeyedTransient allows you to resolve a specific implementation using a unique key such as a string, enum, or other object.

Syntax

builder.Services.AddKeyedTransient<IMessageService, EmailService>("email");
builder.Services.AddKeyedTransient<IMessageService, SmsService>("sms");

Resolving a Keyed Service

You can inject a specific implementation using the [FromKeyedServices] attribute.

public class NotificationController : ControllerBase
{
    private readonly IMessageService _messageService;

    public NotificationController(
        [FromKeyedServices("email")] IMessageService messageService)
    {
        _messageService = messageService;
    }
}

Example

Interface

public interface IMessageService
{
    void Send(string message);
}

Implementations

public class EmailService : IMessageService
{
    public void Send(string message)
    {
        Console.WriteLine($"Email: {message}");
    }
}

public class SmsService : IMessageService
{
    public void Send(string message)
    {
        Console.WriteLine($"SMS: {message}");
    }
}

Registration

builder.Services.AddKeyedTransient<IMessageService, EmailService>("email");
builder.Services.AddKeyedTransient<IMessageService, SmsService>("sms");

Injection

public class NotificationService
{
    private readonly IMessageService _emailService;
    private readonly IMessageService _smsService;

    public NotificationService(
        [FromKeyedServices("email")] IMessageService emailService,
        [FromKeyedServices("sms")] IMessageService smsService)
    {
        _emailService = emailService;
        _smsService = smsService;
    }

    public void Notify()
    {
        _emailService.Send("Welcome!");
        _smsService.Send("OTP: 123456");
    }
}

Lifetime

AddKeyedTransient creates a new instance every time the keyed service is requested, just like AddTransient.

When to Use AddKeyedTransient

  • Register multiple implementations of the same interface.
  • Select an implementation based on a known key.
  • Replace manual service factories or large switch statements.
  • Support scenarios like different payment gateways, notification providers, or storage services.

Comparison

MethodLifetimeSupports KeysUse Case
AddTransientNew instance every requestNoSingle implementation
AddKeyedTransientNew instance every requestYesMultiple implementations with keys
AddScopedOne instance per requestNoRequest-scoped services
AddKeyedScopedOne instance per requestYesKeyed request-scoped services
AddSingletonOne instance for application lifetimeNoShared services
AddKeyedSingletonOne shared instance per keyYesShared keyed services
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