Easy Pagination for Entity Framework in 3 steps

[giscus[bot]]

Easy Pagination for Entity Framework in 3 steps

Pagination is the process of dividing a set into discrete pages. In the context of Entity Framework, that means we are only getting a certain amount of entries from the database.
And we will implement a very easy solution to make that happen in 3 steps. The result will look like this:
var pagedList = DbContext.BlogPosts.ToPagedList(page: 1, pageSize: 5);

https://steven-giesel.com/blogPost/09285b33-79e6-4879-95e0-35aeae5fbcc6

[VictorioBerra]

Thanks for sharing this. It's nice to see a detailed implementation with discussion around how/why choices were made.

Just curious, have your see this? https://github.com/dncuug/X.PagedList

[linkdotnet]

Hey, thanks for the tip.

Actually, yes, I do know that library. It was more or less the reason for that blog post. Initially, I used that library and you might see that the API is almost the same. I found it has some downsides:

• It seems not really maintained anymore (in 1 year not much of commits)
• It uses Task.Run(() => ToList) to mimic async operations. And I found there is a better way if you tailor-make the extension method to EF, RavenDb, ...
• It seems a bit too complex for my use case.

So I let myself get inspired and did it on my own. For the blog itself, the use cases are manageable so I went down the road and implemented a very simple version on my own. Maybe someone can learn something from that, so I published the result :D

[piskov]

Every article using skip/take for pagination should contain big red disclaimer:

T H I S   W I L L   G E T   S L O W   A N D   Y O U ‘ L L   G E T   H U R T :-)

Why? Such code will work fast only while total number of suitable items in DB is not very big. Which is defcon-1 level threat, as problems will arise only when your app becomes used on daily basis for a while.

Suppose user will eventually get to a point where they have, for example, 1000 items and you need to show last 20.

Skip(980).Take(20) seems innocent enough until you realize that in order to get that 20, DB still must scan every single one of 980 before it.

So one should skip offset pagination and take (just couldn’t resist the pun) keyset pagination — with multiple pagination keys if needed — as soon as possible.

Some quickstarter links from .NET Data team:

• Intro into keyset pagination
• Youtube discussion