/// <summary>Constructs the query</summary>
/// <param name="query">The query.</param>
/// <param name="filter">The filter.</param>
/// <typeparam name="T">The source type</typeparam>
/// <typeparam name="T2">The result type</typeparam>
/// <returns>The query</returns>
protected static IQueryable <T2> ConstructQuery <T, T2>(IQueryable <T> query, IQueryFilter <T> filter)
where T : PersistableModel <T>
{
(query as ObjectQuery).MergeOption = MergeOption.OverwriteChanges;
if (filter == null)
{
return(query as IQueryable <T2>);
}
query = filter.GetFilterExpressions().Aggregate(query, (current, q) => current.Where(q));
var f2 = filter as IQueryFilter <T, T2>;
var q2 = query.Select <T, T2>(f2 == null ? null : f2.GetSelectExpression());
if (f2 != null && f2.ShouldApplyDistinct())
{
q2 = q2.Distinct();
}
if (filter.RecordsAvailable == null)
{
filter.RecordsAvailable = q2.Count();
}
q2 = filter.GetIncludeExpressions().Aggregate(q2, (current, e) => current.Include(e));
var orderBy = filter.GetSortExpressions().FirstOrDefault();
if (orderBy != null)
{
q2 = q2.OrderBy(orderBy).ThenBy(filter.GetSortExpressions().Skip(1));
}
if (filter.FirstRecordDesired != null)
{
q2 = q2.Skip(filter.FirstRecordDesired.Value);
}
if (filter.RecordsDesired != null)
{
q2 = q2.Take(filter.RecordsDesired.Value);
}
return(q2);
}