C# Feature – LINQ query expressions

Overview

Query expressions provide a declarative syntax for composing queries that the compiler translates to method calls.

Introduced In

C# 3 (2007)

Before

var adults = people.Where(p => p.Age >= 18).Select(p => p.Name);

After

var adults = from p in people
             where p.Age >= 18
             select p.Name;

Annotated Example

var grouped = from p in people
              group p by p.City into g
              orderby g.Key
              select new { City = g.Key, Count = g.Count() };

Gotchas & Best Practices

• Prefer method syntax for complex lambdas; mix and match as needed.
• Be mindful of deferred execution.

Related Features

• Lambda expressions
• Extension methods
• IEnumerable vs IQueryable
• Generics & LINQ

Version Notes

• Works with anonymous types and var.