Artigo LINQ #1: Utilizando todos os métodos

Program.cs

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

namespace ArtigoLinqParteUm
{
    class Program
    {
        static void Main(string[] args)
        {
            var students = new List<Student>
            {
                new Student("Luis", 980),
                new Student("Felipe", 650),
                new Student("Dev", 340),
            };

            var luis = students.SingleOrDefault(s => s.Name == "Luis");
            var richard = students.SingleOrDefault(s => s.Name == "Richard"); // Retorna null
            // var richardException = students.Single(s => s.Name == "Richard"); // Lança InvalidOperationException

            var firstWithOver600Grade = students.First(s => s.Grade > 600);
            var firstWith1000Grade = students.FirstOrDefault(s => s.Grade == 1000); // Retorna null
            // var firstWith1000GradeException = students.First(s => s.Grade == 1000); // Lança InvalidOperationException

            var allStudentsOver500Grade = students.Where(s => s.Grade > 500);

            foreach (var student in allStudentsOver500Grade)
            {
                Console.WriteLine($"Name: {student.Name}, Grade: {student.Grade}");
                // Imprime duas linhas
                // Name: Luis, Grade: 980
                // Name: Felipe, Grade: 650
            }
        }
    }
}