Question

I have a list of items.
I have to select item with minimum difference between two of its properties.

Eg : Student { string Name, int ScoredMarks, int TotalMarks }
Note : Total marks will not be the same for all students.
I have to select the student with least difference of TotalMarks and ScoredMarks.
I was able to do this way

int minDiff = students.Min(x => (x.TotalMarks - x.ScoredMarks));
var result = from s in students
             where s.TotalMarks - s.ScoredMarks == minDiff
             select s;

Can i achieve it in a single statement? What would be the perfomance of doing this way?
which would be optimistic

Answer 1

You can use Math.Abs to get the absolute difference, order by it and take the first.

Student minDiff = students
        .OrderBy(x => Math.Abs(x.TotalMarks - x.ScoredMarks))
        .FirstOrDefault();
if(minDiff != null)
{
     // ...
}

If you want the best performance you should use MinBy of Skeets MoreLinq. My approach needs to order all items by the value before it takes the one with the lowest difference.

If I have to select all students with minimum differnce i.e what if i have more than one student with same minimum difference.

Then you could use GroupBy:

var minDiffGroup = students
            .GroupBy(x => Math.Abs(x.TotalMarks - x.ScoredMarks))
            .OrderBy(g => g.Key)
            .FirstOrDefault();
foreach(Student student in minDiffGroup)
{
    // ...
}