BI Developer Extensions hanging Visual Studio while walking installed extensions on UI thread

[davkean]

Describe the bug
I'm from the Visual Studio performance team and our telemetry is showing us that BI Developer Extensions extension is causing Visual Studio responsiveness issues by walking all installed extensions while on the UI thread. This has caused Visual Studio to freeze the following amounts over the past 21 days:

Blame	Expressed Hits	Total Hits	Duration (75th Percentile)	Delayed Mouse Clicks	Delayed Key Strokes
bidshelper2019.dll!BIDSHelper.BIDSHelperPackage.OriginalInitialize	132	892	5.10 sec	126	7

Expressed delays are situations where the UI hung while within this method and it interrupted/prevented users mouse or keyboard input. Total hits are all the times the UI hung while within this method, regardless of whether input was interrupted.

The lines of code in question are these:

https://github.com/BIDeveloperExtensions/bideveloperextensions/blob/master/BidsHelperPackage.cs#L165-L208

Version/To Reproduce
This data comes our telemetry system, so we do not have any information on the versions of BI Developer Extensions or any dlls involved in this problem. We also have no understanding of the steps involved to reproduce the above situation other than the fact this data was just captured from real world usage.

Expected behavior
This code should avoid performing this operation on the UI thread. IVsExtensionManager is free-threaded and can be accessed on a background thread, move the SwitchToMainThreadAsync to after it, or introduce a new method that does something like this:

private async Task WalkExtensionsAsync()
{
    await TaskScheduler.Default;

    var em = await  GetServiceAsync<SVsExtensionManager, IVsExtensionManager>(); // NOTE the use of GetServiceAsync, not GetService

    foreach (Microsoft.VisualStudio.ExtensionManager.IInstalledExtension i in em.GetInstalledExtensions())
    { 
      ...
    }
}