linq distinct query? - linq

Question

I need a little help with Linq i have a DB table with restourants tables in it. In the DB i have "TableNumber, Floor , RestaurantID" I would like to get list of all floors. For example if i have this list:
TableNumber, Floor , RestaurantID
10 1 1
11 1 1
12 2 1
13 2 1
14 3 1
I would like to get only "1,2,3".
Right now the method returns all rows.
public IEnumerable<ListPad.Item> GetFloorsListPads(SSF.ART.Key restaurant_id)
{
return from restaurant_floor in EnterpriseTouchRestaurantApplication.TouchRestaurant.AllRestaurantTables
where restaurant_floor.RestaurantID == restaurant_id && restaurant_floor.Active == true
orderby restaurant_floor.Floor
select new ListPad.Item()
{
Color = Color.SkyBlue,
Text = string.Format("{0}", restaurant_floor.Floor),
Tag = restaurant_floor
};
}
Thanks for all the help in advance.

Answer 1

You need either one or two things, depending of whether or not ListPad.Item defines equality (by overriding Equals and GetHashCode) in the way you describe. If so, then adding .Distinct() to your query will give you the distinct items. If not, you can do it one of three ways.
Return an anonymous type, call Distinct on it, and map to the actual type (lazy way)
Implement IEquatable on ListPad.Item, overriding Equals and GetHashCode (you'll need to research how to properly implement GetHashCode so it matches your equality conditions)
Define an IEqualityComparer<ListPad.Item> that defines your equality.
1 is the lazy way but is less coding. 2 is handy if your conditions define equality for ALL uses of ListPad.Item (not just this particular scenario). 3 separates the equality check from the actual type, which is handy if you have other cases where equality would be defined differently.