Use of Let keyword

Posted by Rajesh_Kumar under LINQ category on | Points: 40 | Views : 459
The LET clause allows us to store a result of an expression inside a query expression and use it on the remaining part of the query.
A let clause is useful when the query is using an expression multiple times in a query or if we simply want to create an short alias to a very long variable or property name.

For Example:

We will create a Person class which will contain two properties as FirstName and LastName,so our Person class will look like as:

public class Person
public string FirstName { get; set; }
public string LastName { get; set; }

Not in any event write:

List<Person> obj_persons = new List<Person>
new Person { FirstName="Rajesh",LastName="Sathua" },
new Person { FirstName="Vinod",LastName="Shinde" },
new Person { FirstName="Preeti",LastName="Patle" },
new Person { FirstName="Rutu",LastName="Dixit" }

var query = from obj in obj_persons
let fullName = obj.FirstName + string.Empty + obj.LastName
select new { FullName = fullName };

foreach (var person in query)
Response.Write(person.FullName + "<br/>");

Rajesh Sathua
Vinod Shinde
Preeti Patle
Rutu Dixit

Now we can again simplify above query as:

query = obj_persons.Select(p => new { fullName = p.FirstName + string.Empty + p.LastName })
.Select(p => new { FullName = p.fullName });

foreach (var person in query)
Response.Write(person.FullName + "<br/>");

Output would be the same as above.

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