C# webapi send data after Return

Question

I have an API that returns a list of shops from my database along with shops from Google Places API.

 IEnumerable<ShopInOfferDetails> modelApi = null;
 IEnumerable<ShopInOfferDetails> modelDb = null;

            await new TaskFactory()
                .StartNew(() =>
                {
                    modelApi = Service.GetShopsFromGoogleApi(g);

                })
                .ContinueWith(x =>
                {
                    modelDb = Service.GetShopsFromDb(g);
                });


var model = modelApi.Concat(modelDb);    
return model;

The thing is that it takes too long to get and process the results from Google API (I am doing some more work at the background) and I wonder if there is a way to get the first data from my database - to return this data to the client and only then to get more data from Google Api and Return again - in such way the client gets the first result fast and then the rest from Google API.

Both your calls do IO. One for the DB and one for Google. I'd suggest invoking them concurrently by using their naturally async API's, such are offered via HttpClient and many ORMs. Then you could await Task.WhenAll on both. Alternatively, @Damir's suggestion for creating two different calls may also work if you want to show the end user a result ASAP. — Yuval Itzchakov
– Yuval Itzchakov, Commented Apr 12, 2015 at 16:29

Damir Arh · Accepted Answer · 2015-04-12 16:01:39Z

1

If I were you, I would create 2 different web API methods and call both of them asynchronously from the client. When each one of them returns, the client can immediately show the results - this would create the desired effect: the user would first see the results from the database and then the slower ones from Google API.

answered Apr 12, 2015 at 16:01

Damir Arh

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1 Comment

Eyal Over a year ago

I was thinking about this option but I would like to control the number of the results - If I get enough from my database I won't return from Google. If I won't find the solution that what I will do.

Antony Koch · Accepted Answer · 2015-04-12 16:22:55Z

0

I'd refactor this a bit:

List<ShopInOfferDetails> items = new List<ShopInOfferDetails>();

List<Task<IEnumerable<ShopInOfferDetails>>> tasks = new List<Task<IEnumerable<ShopInOfferDetails>>>();
var task1 = Task.Run(() => {
    items.AddRange(Service.GetShopsFromGoogleApi(g));
    });
tasks.Add(task1);
var task2 = Task.Run(() => {
    items.AddRange(Service.GetShopsFromDb(g));
    });
tasks.Add(task2);

Task.WaitAll(tasks.ToArray());

return items;

answered Apr 12, 2015 at 16:22

Antony Koch

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