Let's say I have a Person record in a database, and there's an Age field for the person.
Now I have a page that allows me to filter for people in certain age ranges.
For example, I can choose multiple range selections, such as "0-10", "11-20", "31-40".
So in this case, I'd get back a list of people between 0 and 20, as well as 30 to 40, but not 21-30.
I've taken the age ranges and populated a List of ranges that looks like this:
class AgeRange
{
int Min { get; set; }
int Max { get; set; }
}
List<AgeRange> ageRanges = GetAgeRanges();
I am using LINQ to SQL for my database access and queries, but I can't figure out how query the ranges.
I want to do something like this, but of course, this won't work since I can't query my local values against the SQL values:
var query = from person in db.People
where ageRanges.Where(ages => person.Age >= ages.Min && person.Age <= ages.Max).Any())
select person;
You could build the predicate dynamically with PredicateBuilder
:
static Expression<Func<Person, bool>> BuildAgePredicate(IEnumerable<AgeRange> ranges)
{
var predicate = PredicateBuilder.False<Person>();
foreach (var r in ranges)
{
// To avoid capturing the loop variable
var r2 = r;
predicate = predicate.Or (p => p.Age >= r2.Min && p.Age <= r2.Max);
}
return predicate;
}
You can then use this method as follows:
var agePredicate = BuildAgePredicate(ageRanges);
var query = db.People.Where(agePredicate);
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