C# LINQ

LINQ (Language Integrated Query) is uniform query syntax in C# and VB.Net
to save and retrieve data from different sources. It is integrated in C#
or VB, thereby eliminating the impedance mismatch between programming
languages and databases, as well as providing a single querying interface
for different types of data sources.

For example, SQL is a Structured Query Language to save and retrieve data
from the database the same way LINQ is a structured query syntax built in
C# and VB.Net to save and retrieve data from different types of data
sources like an Object Collection, an SQL server database,
XML, a web service etc.

Learn LINQ step by step in LINQ tutorials section.

Lamda Expression

C# 3.0/.Net 3.5 introduced lamda expression along with LINQ.
Lambda expression is a shorter way of representing anonymous
method using some special syntax.

s => s.age > 18;