Useful extension methods for Lists in C#

ListExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;

public static class ListExtensions
{
	public static T MaxBy<T, U>(this IEnumerable<T> data, Func<T, U> f) where U : IComparable
	{
		if (data.Count() == 0) throw new ArgumentException($"Cannot get the max of an empty list.");
		T best = data.First();
		U bestValue = f(best);
		foreach (var entry in data)
		{
			U entryValue = f(entry);
			if (entryValue.CompareTo(bestValue) > 0)
			{
				best = entry;
				bestValue = entryValue;
			}
		}
		return best;
	}

	public static int MaxByIndex<T, U>(this IEnumerable<T> data, Func<T, U> f) where U : IComparable
	{
		if (data.Count() == 0) throw new ArgumentException($"Cannot get the max of an empty list.");
		int bestIndex = 0;
		T best = data.First();
		U bestValue = f(best);
		int idx = 0;
		foreach (var entry in data)
		{
			U entryValue = f(entry);
			if (entryValue.CompareTo(bestValue) > 0)
			{
				bestIndex = idx;
				best = entry;
				bestValue = entryValue;
			}
			++idx;
		}
		return bestIndex;
	}

	public static T MinBy<T, U>(this IEnumerable<T> data, Func<T, U> f) where U : IComparable
	{
		if (data.Count() == 0) throw new ArgumentException($"Cannot get the min of an empty list.");
		T best = data.First();
		U bestValue = f(best);
		foreach (var entry in data)
		{
			U entryValue = f(entry);
			if (entryValue.CompareTo(bestValue) < 0)
			{
				best = entry;
				bestValue = entryValue;
			}
		}
		return best;
	}

	public static int MinByIndex<T, U>(this IEnumerable<T> data, Func<T, U> f) where U : IComparable
	{
		if (data.Count() == 0) throw new ArgumentException($"Cannot get the min of an empty list.");
		int bestIndex = 0;
		T best = data.First();
		U bestValue = f(best);
		int idx = 0;
		foreach (var entry in data)
		{
			U entryValue = f(entry);
			if (entryValue.CompareTo(bestValue) < 0)
			{
				bestIndex = idx;
				best = entry;
				bestValue = entryValue;
			}
			++idx;
		}
		return bestIndex;
	}

	public static T Pop<T>(this IList<T> data)
	{
		if (data.Count() == 0) throw new ArgumentException($"Cannot pop an element of an empty list.");
		int idx = data.Count - 1;
		T value = data[idx];
		data.RemoveAt(idx);
		return value;
	}

	public static string ToCommaSeparatedString<T>(this IEnumerable<T> data)
	{
		return string.Join(", ", data);
	}

	public static HashSet<T> ToHashSet<T>(this IEnumerable<T> data)
	{
		return new HashSet<T>(data);
	}
}