Don't call GetService in Package constructors

[AlexEyler]

Calling GetService in Package constructors is a common place for failures - there's no guarantee that the service provider will be properly set up by the time the Package is created.

Instead, the GetService call should be done in Initialize (or InitializeAsync, after switching to the main thread).

[AArnott]

@AlexEyler was this GetService call you saw the Package.GetService method, or were you talking about the static global service provider's GetService method?

A sample snippet of a violation would be helpful.

[AlexEyler]

In this case it was the global provider - I saw something like this in a Package ctor:

var cm = Microsoft.VisualStudio.Shell.Package.GetGlobalService(typeof(SComponentModel)) as IComponentModel;
var item = cm.DefaultExportProvider.GetExport<Item>().Value;
item.Event += EventHandler;

[AArnott]

Interesting. And why is GetGlobalService not safe to call from a package's ctor?

[AlexEyler]

Hmm - I'm not sure. I thought there wasn't a guarantee that the service provider would be fully initialized when the constructor is called. From this doc:

Let's add a message that lets us know that the VSPackage has loaded. We use the VSPackage's Initialize() method to do this, because you can get Visual Studio services only after the VSPackage has been sited. (For more information about getting services, see How to: Get a Service.) Replace the Initialize() method of FirstPackage with code that gets the SVsUIShell service, gets the IVsUIShell interface, and calls its ShowMessageBox method.

[AArnott]

I think that document is talking about how a package cannot get services until sited based on the fact that it has no service provider to query. But global statics get around that (for better or worse). The global service provider starts working before any Package is loaded (as necessary, since every package is chained to it). So AFAIK there's nothing wrong with querying for services from a package's constructor, strictly speaking.

Of course, we'd prefer all packages to be async and to query for services from their InitializeAsync method instead.