LINQ to objects

LINQ is of different types based on the source of data.For example for querying in-memory data sources or collections LINQ to objects is used.

LINQ to objects is used for querying collections such as List<T>.Any collection which implements IEnumerable<T> or IEnumerable interfaces can be queried using LINQ.

Arrays can be querid using LINQ queries since it implements IEnumerable.

Below is a sample LINQ to Objects query.

string[] users = { "Marc","John","Robin","Prashant" };
var lstUsers = from user in users
where user="Marc"
select user;

This is called query expression.

We can also write the above query using query operators:

var lstUsers =
users.Where(user => user=="Marc")
.Select(user);

In the  above example we have used the following query operators:

• Where   Where operator is used to filter the collection based on the given condition.In this example we have specified the condition that user should be equal to Marc
• Select  Select operator is used to project or return values as specified.Here we are returning the user.The return values of the operator is also IEnumerable<T>.

Following are some of the main LINQ query operators:

Use	Query operator
Filtering	Where
Projection	Select
Partitioning	Skip, SkipWhile, Take, TakeWhile
Ordering	OrderBy, OrderByDescending,ThenBy
Grouping	GroupBy
Set	Intersect

 

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