what is the purpose of registering the same service more than once?

Question

I recently run upon a net core project with the current configuration:

services.AddTransient<Service1>();
services.AddSingleton<Service1>();

Where Service1 was a class. What could possibly be the purpose of this? Or its just a mistake? Is there any way to choose whether to use a new instance of the service or the singleton dynamically?

You can check your question at: https://stackoverflow.com/questions/38138100/addtransient-addscoped-and-addsingleton-services-differences — Ferrari, Feb 21 '20 at 14:45
I know the diferences. I was wandering why there are used BOTH — kkica, Feb 21 '20 at 14:46
It is literally like that? I only imagine the usage in runtime when the context has been changed somehow and you need to use a singleton — Michał Jarzyna, Feb 21 '20 at 14:46
So this is a mistake probably, IoC would use Singleton registration as the last one — Michał Jarzyna, Feb 21 '20 at 14:47

score 2 · Accepted Answer · answered Feb 21 '20 at 14:46

2

The last registration "wins" so your Service1 type will be registered as a singleton given your current code.

If you change the order of the calls, it's going to be registered as a transient dependency. But don't do both. Choose one lifetime per type.

answered Feb 21 '20 at 14:46

mm8

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adding to the above, if you use TryAdd instead of Add, it will keep the first registration https://learn.microsoft.com/en-us/dotnet/api/microsoft.extensions.dependencyinjection.extensions.servicecollectiondescriptorextensions.tryadd?view=dotnet-plat-ext-3.1 – Jonathan Busuttil Feb 24 '20 at 10:56

what is the purpose of registering the same service more than once?

1 Answers1