# Externally Managed Mode


> [!WARNING]
> In NServiceBus version 10.2.0 and above, externally managed mode is no longer a relevant concept, as integration with the Microsoft .NET Host is integrated directly into NServiceBus.
>
> See the documentation on [hosting with Microsoft.Extensions.Hosting](/nservicebus/hosting/core-hosting.md) or the [NServiceBus version 10 to 11 upgrade guide](/nservicebus/upgrades/10to11/index.md) for more information.

### Configuring the endpoint

This sample configures an endpoint to use [externally managed mode](/nservicebus/dependency-injection/index.md#modes-of-operation-externally-managed-mode) with [Microsoft's dependency injection container](https://www.nuget.org/packages/Microsoft.Extensions.DependencyInjection) and registers some dependencies.

<!-- snippet: ContainerConfiguration -->

```cs
// ServiceCollection is provided by Microsoft.Extensions.DependencyInjection
var serviceCollection = new ServiceCollection();

// most dependencies may now be registered
serviceCollection.AddSingleton<Greeter>();
serviceCollection.AddSingleton<MessageSender>();

// EndpointWithExternallyManagedContainer.Create accepts an IServiceCollection,
// which is inherited by ServiceCollection
var endpointWithExternallyManagedContainer = EndpointWithExternallyManagedContainer
    .Create(endpointConfiguration, serviceCollection);

// if IMessageSession is required as dependency, it may now be registered
serviceCollection.AddSingleton(p => endpointWithExternallyManagedContainer.MessageSession.Value);
```

<!-- endsnippet -->

### Injecting dependencies into handlers

Registered dependencies may be injected into message handlers using constructor injection:

<!-- snippet: InjectingDependency -->

```cs
public class MyHandler(Greeter greeter) : IHandleMessages<MyMessage>
{
    public Task Handle(MyMessage message, IMessageHandlerContext context)
    {
        greeter.SayHello();
        return Task.CompletedTask;
    }
}
```

<!-- endsnippet -->

### Injecting the message session into other types

When `IMessageSession` has been registered as shown above, it may be injected into other types using constructor injection:

<!-- snippet: InjectingMessageSession -->

```cs
public class MessageSender(IMessageSession messageSession)
{
    public Task SendMessage()
    {
        var myMessage = new MyMessage();
        return messageSession.SendLocal(myMessage);
    }
}
```

<!-- endsnippet -->

> [!NOTE]
> An `IMessageSession` may only be injected by the container _after the endpoint has been started_.