private async Task DoSearch(string searchTerm, CancellationToken token)
{
token.ThrowIfCancellationRequested();
IsSearching = true;
token.ThrowIfCancellationRequested();
searchResults.Clear();
token.ThrowIfCancellationRequested();
var results = await repository.FindAsync(searchTerm);
token.ThrowIfCancellationRequested();
await searchResults.AddAllAsync(results.Keys);
token.ThrowIfCancellationRequested();
await TaskEx.WhenAll(results.Values);
token.ThrowIfCancellationRequested();
IsSearching = false;
}