C#: relational queries with LINQ join and group

LINQ (Language Integrated Query) brings relational-style queries into C#. Its query syntax mirrors SQL: from names a row, join ... on ... equals ... matches rows by key, orderby sorts, and select shapes the result. The same operations are available as methods such as Join, GroupBy, and OrderBy.

using System;
using System.Linq;

class Program {
  static void Main() {
    var departments = new[] { new { Id = 1, Title = "Eng" }, new { Id = 2, Title = "Ops" } };
    var staff = new[] {
      new { Name = "Ada", Dept = 1, Salary = 120 },
      new { Name = "Bo", Dept = 2, Salary = 90 },
      new { Name = "Cy", Dept = 1, Salary = 100 },
      new { Name = "Di", Dept = 3, Salary = 80 },
    };

    var joined = (from e in staff
                  join d in departments on e.Dept equals d.Id
                  orderby e.Name
                  select new { e.Name, d.Title, e.Salary }).ToList();
    foreach (var row in joined) {
      Console.WriteLine(row.Name + " " + row.Title + " " + row.Salary);
    }

    var totals = joined.GroupBy(r => r.Title)
                       .Select(g => g.Key + ": " + g.Sum(r => r.Salary))
                       .OrderBy(text => text);
    foreach (var line in totals) {
      Console.WriteLine(line);
    }
  }
}

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