LINQ - Query Syntax, Method Syntax and Lamda Expressions

There are two basic ways to write a LINQ query to IEnumerable collection or IQueryable data sources.

• Query Syntax - aka Query Expression Syntax 
• This is similar to SQL (Structured Query Language) for the database.
• The LINQ query starts with the From clause and ends with the Select or GroupBy clause.

• Implicitly typed variable - var can be used to hold the result of the LINQ query.
• You can use various query operators (filtering, joining, grouping. sorting etc.) to construct the desired result.

• Method Syntax  - aka Method extension syntax or Fluent
• Uses extension method included in the Enumerable and Queryable static class.

 

• Method syntax comprises of extension methods and Lamda expressions.
• Implicitly typed variable - var can be used to hold the result of the LINQ query. 

Lamda Expressions - A shorter way of representing anonymous methods using special syntax. In the above example. 

• Syntax: parameter => body expression

In below example i is the parameter , => is the Lamda operator, and (i%2) == 0 is the body expression.

• Can have zero parameters.
• Can have multiple parameters.
• Can have multiple statements in body expression.
• Can be assigned to generic delegates Func, Acton or Predicate.
• Can be invoked same way as delegate.