Question

How would you implement paging in a LINQ query?
Actually for the time being, I would be satisfied if the sql TOP function could be imitated. However, I am sure that the need for full paging support comes up sooner later anyway.

var queryResult = from o in objects
                  where ...
                  select new
                      {
                         A = o.a,
                         B = o.b
                      }
                   ????????? TOP 10????????

Answer 1

You’re looking for the Skip and Take extension methods. Skip moves past the first N elements in the result, returning the remainder; Take returns the first N elements in the result, dropping any remaining elements.

See Microsoft’s documentation for more information on how to use these methods:
https://learn.microsoft.com/en-us/dotnet/framework/data/adonet/sql/linq/return-or-skip-elements-in-a-sequence

If your pageNumber starts at 0 (decrease per 1 as suggested in the comments), you could do it like this:

int numberOfObjectsPerPage = 10;
var queryResultPage = queryResult
  .Skip(numberOfObjectsPerPage * pageNumber)
  .Take(numberOfObjectsPerPage);

If pageNumber starts at 1 (as suggested by @Alvin), then you coudld o it like this:

int numberOfObjectsPerPage = 10;
var queryResultPage = queryResult
  .Skip(numberOfObjectsPerPage * (pageNumber - 1))
  .Take(numberOfObjectsPerPage);