How to Sort List of Objects in C# Easily

To sort a list of objects in C#, use List.Sort() with a custom comparison method or implement IComparable in your object class. You can also use List.Sort((x, y) => x.Property.CompareTo(y.Property)) for quick sorting by a property.

Syntax

You can sort a list of objects in C# using the List.Sort() method. It can be used in three main ways:

• Default sorting: Your object class implements IComparable.
• Custom comparer: Pass an IComparer implementation to Sort().
• Lambda expression: Use a lambda to define the comparison inline.

Example syntax for lambda sorting:

list.Sort((x, y) => x.Property.CompareTo(y.Property));

csharp

list.Sort((x, y) => x.Property.CompareTo(y.Property));

Example

This example shows how to sort a list of Person objects by their Age property using a lambda expression with List.Sort().

csharp

using System;
using System.Collections.Generic;

class Person
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override string ToString() => $"{Name}, {Age}";
}

class Program
{
    static void Main()
    {
        var people = new List<Person>
        {
            new Person { Name = "Alice", Age = 30 },
            new Person { Name = "Bob", Age = 25 },
            new Person { Name = "Charlie", Age = 35 }
        };

        // Sort by Age
        people.Sort((x, y) => x.Age.CompareTo(y.Age));

        foreach (var person in people)
        {
            Console.WriteLine(person);
        }
    }
}

Output

Bob, 25
Alice, 30
Charlie, 35

Common Pitfalls

Common mistakes when sorting lists of objects include:

• Not implementing IComparable or providing a comparer, causing Sort() to fail.
• Using incorrect comparison logic that does not return a negative, zero, or positive integer properly.
• Sorting by a property that can be null without handling nulls, leading to exceptions.

Example of a wrong comparison and the correct way:

csharp

/* Wrong: returns boolean instead of int */
// people.Sort((x, y) => x.Age > y.Age);

/* Correct: returns int as expected */
// people.Sort((x, y) => x.Age.CompareTo(y.Age));

Quick Reference

Method	Description	Example
Implement IComparable	Define natural order inside the class	class Person : IComparable { public int CompareTo(Person other) { return Age.CompareTo(other.Age); } }
Use List.Sort with IComparer	Pass a comparer object to Sort	list.Sort(new AgeComparer());
Use List.Sort with Lambda	Inline comparison by property	list.Sort((x, y) => x.Age.CompareTo(y.Age));

Key Takeaways

Use List.Sort with a lambda expression for quick and easy sorting by object properties.

Implement IComparable in your class for natural default sorting.

Always ensure your comparison returns an int: negative, zero, or positive.

Handle null values in properties to avoid runtime errors during sorting.