Paginator.EntityFrameworkCore

Asynchronous & Synchronous pagination of queries to your data store using EntityFrameworkCore. With the help of some simple to use extension methods, querying portions/chunks of data just gets easier.

Use Cases

Suppose we have 5,000 rows in the Employee table, lets look at a few different ways to query chunks of that data as efficiently as possible and return the result in a paginated format.

This code snippet represents our connection to the table whilst telling EF not to track the results of the query, inorder to get some slight performance improvement.

IQueryable<Employee> employees = _context.Set<Employee>().AsNoTracking(); 

Example-I: Page 2, Perpage 20

Internally translates to skipping the first page and taking the next 20 records that follow.

PagedResult<Employee> paged = employees.Paginate(2,20);
Console.WriteLine(paged);
// Page: 2 Perpage: 20 Totalpages: 250 TotalItems: 5,000

Example-II: Page 2, Perpage 20, Asynchronously

await call to .PaginateAsync and optionally pass a CancellationToken as shown below. The result of this query will be the same as that of the previous example.

An OperationCanceledException is thrown if cancellation is requested on the specified cancellationToken.

var tokenSource = new CancellationTokenSource();

PagedResult<Employee> paged = await employees.PaginateAsync(2,20, token: tokenSource.Token);

Console.WriteLine(paged);
// Page: 2 Perpage: 20 Totalpages: 250 TotalItems: 5,000

Skip count & perfomance concerns of .Count()

We all know that pagination is a two step procedure, with one counting the total number of items in a sequence, and the second that picks N items from that sequence.

Sometimes, the .Count() query doesn't perform very well especially when dealing with large datasets, or your use case might not require knowing TotalPages and TotalItems. We can tell the pagination method to ignore doing the count operation as illustrated in the examples below.

Example-III: Page 2, Perpage 20, Skipping Count

To ignore count, just pass true as a parameter to the param: skipCount which comes right after perpage.

Take a look at the console output to spot the difference.

PagedResult<Employee> paged = employees.Paginate(2,20, skipCount: true);
Console.WriteLine(paged);
// Page: 2 Perpage: 20 Totalpages: 1 TotalItems: 20

Contributions

Suggestions & improvements are welcome.