如何使用LINQ获取最低值的项目？

Question

I have below class -

  public class Test
    {
        public string TestServerName;
        public string TestApplicationRunning;
        public bool IsAvailable;
        public long Counter;
    }

How to get the items with lowest counter value using LINQ?

Suppose lowest counter value is 0 in all items then LINQ should return all items with Counter value 0.There can be more then 1 items with counter value minimum.

Answer 1

You can use Min extension method and then filter source with the help of Where extension method:

var minValue = source.Min(x => x.Counter);
var result = source.Where(x => x.Counter == minValue).ToList();

Don't forget to include Systme.Linq namespace. BTW, with this approach, you will execute two queries to the source.

Answer 2

You could also do :

source.GroupBy(x=>x.Counter)
      .OrderBy(x=>x.Key)
      .Take(1)
      .Select(x=>x).ToList();

though it's not as obvious as Fᴀʀhad's solution :)

Answer 3

Try this example:

List<Test> lstTests = new lstTests();
Test test1 = new Test();
Test test2 = new Test();
Test test3 = new Test();

test1.Counter = 3;
test2.Counter = 4;
test3.Counter = 3;

lstTests.Add(test1);
lstTests.Add(test2);
lstTests.Add(test3);


var valMin = lstTests.Min(m => m.Counter);
var results = source.Where(x => x.Counter == valMin).ToList();

OR

var result = source.Where(x => x.Counter == valMin).FirstOrDefault();

If u want the first occurance Use FirstOrDefault .

Answer 4

With below query you can find nth lowest value

int ix = 1;
var orderedSource  = source.OrderBy(i => i.counter).Select(y => new { rank =ix++ , value = y });

you pass any value instead of N to get nth lowest value

int N = 4;
var  result  = orderedSource.Where(x=>x.rank == N).FirstOrDefault();
Test testValue = result.value; 

Answer 5

You can use the MinBy (or MaxBy ) extension method from MoreLinq .

As from this issue , the min by functionality change to return IEnumerable of T (if to be more precise: IExtremaEnumerable ) instead of only one T item to:

public static IExtremaEnumerable<TSource> MinBy<TSource, TKey>(this IEnumerable<TSource> source,
        Func<TSource, TKey> selector, IComparer<TKey> comparer)

Usage Example:

using MoreLinq;

IEnumerable<Test> testList = source.MinBy(p => p.Counter);