Top 10 Percentile by salary of results

Question

I have a in-memory List of Job objects, were the Job object has a propery called Salary.

How do I use LINQ or C# to filter this list to only contain the list of jobs with salaries in the top 10 or bottom 10 percentile?

Here is my attempt, which seems to work for me so far:

var tenthPercentileCount = allJobsCount / 10;
var top10PercentileJobs = allJobs
    .OrderByDescending(j => j.Salary.SalaryAmount)
    .Take(tenthPercentileCount)
    .ToList();
var bottom10PercentileJobs = allJobs
    .OrderBy(j => j.Salary.SalaryAmount)
    .Take(tenthPercentileCount)
    .ToList();

Answer 1

First, you'll want to calculate how many entries constitute 10%. You can do this by dividing the size of the list by 10 (and rounding or truncating to get an integer). Let's call this number X.

Next, you'll want to order the list by salaray in descending order. You'll want to take the first X elements in the list. These will be the ones in the top 10%.

To get the bottom 10%, you'll want to skip the first 90% (you can use 9X or subtract X from the full size - one of those might not work as expected) before taking X from the list. Alternately, you could order the list by salary and take the first X.

It would also help to use the System.Linq namespace.

Answer 2

I've built an Extension for removing percentage of a list. all you need to do is order the list before using the extension.

   public static IEnumerable<T> RemoveBeforeAndAfter<T>(this IEnumerable<T> source, int percent, bool removeLast = false, bool removeFirst = false)
    {
        var enumerable = source as IList<T> ?? source.ToList();
        var sourceCount = enumerable.Count();
        var noRemove = Convert.ToInt32(Math.Ceiling((percent / 100D) * sourceCount));
        var remove = new List<T>();
        if (enumerable.Any())
        {
            if (removeLast)
                remove.AddRange(enumerable.Reverse().Take(noRemove));
            if (removeFirst)
                remove.AddRange(enumerable.Take(noRemove));
            return enumerable.Where(x => remove.Any(r => x.Equals(r))).ToList();

        }

        return default(IEnumerable<T>);
    }