Improve your code with LINQ – How to speed up your Xamarin and .Net app
May 10, 2019 | Code Optimization, Guide | No Comments
Usually a desktop platform has a lot of available resources so many developers tend to avoid to improve the quality of their code.On a mobile platform the resources are quite limited and improving the code could make a huge difference. It can transform a slow and annoying app in a great fast and great one.Today, using the code I’ve written for one of my app Tv Series Time Manager, we are going to see how improving the code can make a huge difference in the loading time of your apps.
Improve your code – LINQ is your friend
Tv Series time manager allows you to keep track of your preferred tv series.It uses a public API to get information about all the TV Series created. As you can imagine there are thousands and thousands of Tv Series so we need to handle lists of thousands of items.Every time we launch the app, it searches online updated about the Tv Series you are following (new episodes, release dates, and so on). This can be a quite intensive task as the API we need to call returns a JSON file with more than 34000 items.The first time I’ve written the updated method I had this code:
var localTvShows = LocalData.GetAllTvShows();
var remoteUpdatedTime = await WsData.GetUpdatedShows();
foreach (var info in remoteUpdatedTime)
{
var show = localTvShows.FirstOrDefault(x => x.id == info.Key);
if (show != null && info.Value > show.updated)
{
updateRequired = true;
break;
}
}
if (UpdateRequired)
{
foreach (var info in remoteUpdatedTime)
{
var show = localTvShows.FirstOrDefault(x => x.id == info.Key);
if (show != null && info.Value > show.updated)
{
var remoteserie = await WsData.GetShow(show.id);
SqlHelper.SyncSerie(show, remoteserie);
var episodeList = await WsData.GetEpisodes(show.id);
SqlHelper.SyncEpisodes(show.idLocal, episodeList);
}
}
}I load the local Tv Show followed by the user and the remote Tv Series with the corresponding update time.Inside the first foreach I check if I need to update the local Tv Series.In case I have to update a Tv Series, I use a second foreach to update every local TV Series inside the local Sql database. (To add SQLite database to your app, you can read this tutorial)The code worked pretty well but I wasn’t satisfied by the loading time so I started to look for a way to improve the performances and here I discovered once more that LINQ is our friend.
The new code with LINQ
I decided to use LINQ to evaluate if I have to update a tv series, so I’ve written the code replacing the old one with this:
var seriesToUpdate = from remoteTime in remoteUpdatedTime
join localShow in localTvShows
on remoteTime.Key equals localShow.id
where remoteTime.Key == localShow.id && remoteTime.Value > localShow.updated
select localShow;
if (seriesToUpdate.Any())
{
foreach (var show in seriesToUpdate)
{
var remoteserie = await WsData.GetShow(show.id);
SqlHelper.SyncSerie(show, remoteserie);
var episodeList = await WsData.GetEpisodes(show.id);
SqlHelper.SyncEpisodes(show.idLocal, episodeList);
}
}Speed Test
Now it’s time to see if the new code is really better than the first (Obviously it is 🙂 ). To do so, I’ve divided the code in two parts.
- Evaluate if an update is required (Part A)
- Update the Tv Series (Part B).
To give you the idea of how much time we can save, I’ve enclosed both the code in a for statement repeating the it for 100 times. These are the result:
Part A
- OLD CODE: Elapsed Time: 1077 ms
- NEW CODE: Elapsed Time: 225 ms
Part B
- OLD CODE: Elapsed Time: 590 ms
- NEW CODE: Elapsed Time: 122 ms
Total
- OLD CODE: Elapsed Time: 1667 ms
- NEW CODE: Elapsed Time: 347 ms
Looking at the time spent by the old and new code we went from 1667 ms to 347 ms, saving 1320 ms. The difference is HUGE.From the point of view of a user, saving almost 1.5 seconds makes a massive difference, maybe the difference between keeping your app or uninstalling it.
Conclusion
A mobile device has a limited amount of resources and users don’t like to spend time waiting in front of a loading screen. Even the most useful app, if not optimized will be uninstalled by the users. This is why it’s really important to optimize your code.Today we have seen that with a good use LINQ we can massively reduce the time used by our code.If you like the article, comment and share it!
