Parallel.Invoke does not wait for async methods to complete

Question

I have an application that pulls a fair amount of data from different sources. A local database, a networked database, and a web query. Any of these can take a few seconds t

Answer 1

As you stated in your question, two of your methods query a database (one via sql, the other via azure) and the third triggers a POST request to a web service. All three of those methods are doing I/O bound work.

What happeneds when you invoke Parallel.Invoke is you basically trigger three ThreadPool threads to block and wait for I/O based operations to complete, which is pretty much a waste of resources, and will scale pretty badly if you ever need to.

Instead, you could use async apis which all three of them expose:

1. SQL Server via Entity Framework 6 or ADO.NET
2. Azure has async api's
3. Web request via HttpClient.PostAsync

Lets assume the following methods:

LoadXAsync();
LoadYAsync();
LoadZAsync();

You can call them like this:

spinner.IsBusy = true;
try
{
    Task t1 = LoadXAsync();
    Task t2 = LoadYAsync();
    Task t3 = LoadZAsync();

    await Task.WhenAll(t1, t2, t3);
}
finally
{
    spinner.IsBusy = false;
}

This will have the same desired outcome. It wont freeze your UI, and it would let you save valuable resources.