c# - LINQ to Get Closest Value?

Question

I have a List, MyStuff has a property of Type Float.

There are objects with property values of 10,20,22,30.

I need to write a query that finds the objects closest to 21, in this case it would find the 20 and 22 object. Then I need to write one that finds the object closes to 21 without going over, and it would return the object with a value of 20.

I have no idea where/how to begin with this one. Help?

Thanks.

Update - wow there are so many awesome responses here. Thanks! I don't know which one to follow so I will try them all. One thing that might make this more (or less) interesting is that the same query will have to apply to LINQ-to-SQL entities, so possibly the answer harvested from the MS Linq forums will work the best? Don't know.

Answer 1

Try sorting them by the absolute value of the difference between the number and 21 and then take the first item:

float closest = MyStuff
    .Select (n => new { n, distance = Math.Abs (n - 21) })
    .OrderBy (p => p.distance)
    .First().n;

Or shorten it according to @Yuriy Faktorovich's comment:

float closest = MyStuff
    .OrderBy(n => Math.Abs(n - 21))
    .First();