OrderByNullsLast

Simple C# library to specify whether to place nulls first or last when ordering an enumerable by a key selector with nullable types.

Nuget Package Link

Example

The default behavior of System.Linq.OrderBy would always place null values first. Using the OrderByNullsLast package, it allows us to specify either nulls first, or nulls last, regardless of sort order, without having to create a custom IComparer.

using System.Linq;
using OrderByNullsLast;

public class Element
{
    public Element(double? structVal, string classVal)
    {
        StructValue = structVal;
        ClassValue = classVal;
    }

    public double? StructValue { get; }
    public string ClassValue { get; }
}

var list = new List<Element>
{
    new Element(3, "3"),
    new Element(null, null),
    new Element(1, "1"),
    new Element(2, "2"),
    new Element(null, null)
};

// Selector key type is a nullable struct
list.OrderBy(x => x.StructValue, NullOrder.NullsFirst); // null, null, 1, 2, 3
list.OrderBy(x => x.StructValue, NullOrder.NullsLast); // 1, 2, 3, null, null
list.OrderByDescending(x => x.StructValue, NullOrder.NullsFirst); // null, null, 3, 2, 1
list.OrderByDescending(x => x.StructValue, NullOrder.NullsLast); // 3, 2, 1, null, null

// Selector key type is a class
list.OrderBy(x => x.ClassValue, NullOrder.NullsFirst); // null, null, "1", "2", "3"
list.OrderBy(x => x.ClassValue, NullOrder.NullsLast); // "1", "2", "3", null, null
list.OrderByDescending(x => x.ClassValue, NullOrder.NullsFirst); // null, null, "3", "2", "1"
list.OrderByDescending(x => x.ClassValue, NullOrder.NullsLast); // "3", "2", "1", null, null