Below are my classes. I have a product that contains list of days. Each day has a city property.
I need to create a linq query that will give me the distinct cities that are used on all my products in the system.
I tried something like this but it does not work:
var cities = from product in NHibernateSession.Linq<Product>() select new { city = product.Days.Where(d => d.City != null).Distinct() }; //This returns the day items but i need distinct cities
public class Product : EntityBase
{
public virtual string Name { get; set; }
public virtual IList<ProductDayDefinition> Days { get; set; }
}
public class ProductDayDefinition : EntityBase
{
public virtual Product Product { get; set; }
public virtual City City { get; set; }
}
You need to call the SelectMany
function, which takes a single item and lets you get multiple items from it.
For example:
var cities = NHibernateSession.Linq<Product>()
.SelectMany(p => p.Days)
.Select(p => p.City)
.Where(c => c != null)
.Distinct();
Note that if the City
class doesn't implement Equals
and GetHashCode
correctly, this will return duplicates.
You can do this using query comprehension syntax like this: (Untested)
var cities = (from product in NHibernateSession.Linq<Product>()
from day in product.Days
where day.City != null
select day).Distinct();
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With