/// <summary>
/// Paginates using keyset pagination.
/// </summary>
/// <typeparam name="T">The type of the elements of source.</typeparam>
/// <param name="source">An <see cref="IQueryable{T}"/> to paginate.</param>
/// <param name="builderAction">An action that takes a builder and registers the columns upon which keyset pagination will work.</param>
/// <param name="direction">The direction to take. Default is Forward.</param>
/// <param name="reference">The reference object. Needs to have properties with exact names matching the configured properties. Doesn't necessarily need to be the same type as T.</param>
/// <returns>The modified the queryable.</returns>
/// <exception cref="ArgumentNullException">source or builderAction is null.</exception>
/// <exception cref="InvalidOperationException">If no properties were registered with the builder.</exception>
/// <remarks>
/// Note that calling this method will override any OrderBy calls you have done before.
/// </remarks>
public static IQueryable <T> KeysetPaginateQuery <T>(
this IQueryable <T> source,
Action <KeysetPaginationBuilder <T> > builderAction,
KeysetPaginationDirection direction = KeysetPaginationDirection.Forward,
object?reference = null)
where T : class
{
return(KeysetPaginate(source, builderAction, direction, reference).Query);
}
internal KeysetPaginationContext(
IQueryable <T> query,
IOrderedQueryable <T> orderedQuery,
IReadOnlyList <KeysetPaginationItem <T> > items,
KeysetPaginationDirection direction)
{
Query = query;
OrderedQuery = orderedQuery;
Items = items;
Direction = direction;
}
/// <summary>
/// Paginates using keyset pagination.
/// </summary>
/// <typeparam name="T">The type of the elements of source.</typeparam>
/// <param name="source">An <see cref="IQueryable{T}"/> to paginate.</param>
/// <param name="builderAction">An action that takes a builder and registers the columns upon which keyset pagination will work.</param>
/// <param name="direction">The direction to take. Default is Forward.</param>
/// <param name="reference">The reference object. Needs to have properties with exact names matching the configured properties. Doesn't necessarily need to be the same type as T.</param>
/// <returns>An object containing the modified queryable. Can be used with other helper methods related to keyset pagination.</returns>
/// <exception cref="ArgumentNullException">source or builderAction is null.</exception>
/// <exception cref="InvalidOperationException">If no properties were registered with the builder.</exception>
/// <remarks>
/// Note that calling this method will override any OrderBy calls you have done before.
/// </remarks>
public static KeysetPaginationContext <T> KeysetPaginate <T>(
this IQueryable <T> source,
Action <KeysetPaginationBuilder <T> > builderAction,
KeysetPaginationDirection direction = KeysetPaginationDirection.Forward,
object?reference = null)
where T : class
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (builderAction == null)
{
throw new ArgumentNullException(nameof(builderAction));
}
var builder = new KeysetPaginationBuilder <T>();
builderAction(builder);
var items = builder.Items;
if (!items.Any())
{
throw new InvalidOperationException("There should be at least one property you're acting on.");
}
// Order
var orderedQuery = items[0].ApplyOrderBy(source, direction);
for (var i = 1; i < items.Count; i++)
{
orderedQuery = items[i].ApplyThenOrderBy(orderedQuery, direction);
}
// Filter
var filteredQuery = orderedQuery.AsQueryable();
if (reference != null)
{
var keysetFilterPredicateLambda = BuildKeysetFilterPredicateExpression(items, direction, reference);
filteredQuery = filteredQuery.Where(keysetFilterPredicateLambda);
}
return(new KeysetPaginationContext <T>(filteredQuery, orderedQuery, items, direction));
}
public abstract IOrderedQueryable <T> ApplyThenOrderBy(IOrderedQueryable <T> query, KeysetPaginationDirection direction);
