It does seem like this extension isn't useful. Since it's somewhat harmless we probably won't get to this in 3.0 but I'll label as help wanted because we'd look at a PR here.

Moving the null check to ServiceCollection is probably reasonable since I don't know what it would mean to register a a null descriptor anyway :).

@anurse I would like to contribute this, but before begin, Add method in ServiceCollection.cs is returns void, so We cant do method chaining. But Add method in ServiceCollectionDescriptorExtensions returns ServiceCollection so it enable us to further chain the other method. Is this a concern?

Ah, I see, the original intent of the extension method was possibly to add chaining, but it doesn't work, as we can see.

We could overcome this issue with different method names. When chaining comes into play, a typical naming convention is to use the "With" prefix.

So, we could name the extension methods this way:

• With
• WithScoped
• WithSingleton

and so on.

On the othen hand I don't understand why chaining was not implemented with the TryAdd methods? They simply return void (not even bool).

For consistency I would also propose the following method names when chaining comes into play:

• TryWith
• TryWithScoped
• TryWithSingleton

But I think this should decide someone who has a pretty good overview of the conventions used in .NET Core.

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Anybody around who knows the initial intent of the extension method? If it was chaining, then we should not use Add as a method name as I already noted.

Paging @dotnet/extensions-migration ! This issue has been revived from staleness. Please take a look and route to the appropriate repository.

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