WebExtensionPack.DataStore.HasBeenInstalled C# (CSharp) Method

        public bool HasBeenInstalled(string productId)
        {
            return PreviouslyInstalledExtensions.Contains(productId);
        }

        private IEnumerable <KeyValuePair <string, string> > GetMissingExtensions(IVsExtensionManager manager, DataStore store)
        {
            var installed    = manager.GetInstalledExtensions();
            var products     = ExtensionList.Products();
            var notInstalled = products.Where(product => !installed.Any(ins => ins.Header.Identifier == product.Key)).ToArray();

            return(notInstalled.Where(ext => !store.HasBeenInstalled(ext.Key)));
        }