To retrieve a selective number of elements through a sequence, or page through the sequence, a query expression is used. Query expressions allow us to query a data source and put the results in the desired form. Query expressions provide support for LINQ in F#. A typical use case of pagination is a retail location grid where we see 10-20 stores at a time, based on search criteria. This search of elements can later be expanded based on users' selection of the page number.

As a computation expression, query expressions are similar to sequences. Just like sequences, where to populate a sequence you provide code in a sequence expression, for query expression you specify a predicate, a selection query, or similar code.

To understand query expressions, we will expand upon the datasets used in the preceding file and see some examples. Let's begin by creating a type as follows: