LINQ Syntax
There are two basic ways to write a LINQ query:
- Query
Syntax or Query Expression Syntax
- Method
Syntax or Method extension syntax or Fluent
Query
Syntax:
Query
syntax is similar to SQL (Structured Query Language) for a database. It is
defined within the C# or VB code.
from <range
variable> in <collection>
<filter, joining,
grouping, aggregate operators etc.> <lambda expression>
<select or groupBy
operator> <formulate the result>
Example
int[] numbs = new int[7] { 0, 1, 2, 3, 4, 5, 6 };
var numQry =
where (num % 2) == 0
select num;
Query
Syntax starts with from clause
followed by Range variable. After from clause, you can use different standard
query operations such as filter, group, joins etc. there are 50 standard query
operators available in LINQ. In Above Example we used where operator to filter even numbers. LINQ always ends with select or group by clause. The select is used to get data from source.
You can have whole object or some properties of the object in select section.
LINQ Method Syntax
Method syntax (also known as fluent syntax) uses extension
methods included in the Enumerable or Queryable static class, similar to how you would call the
extension method of any class.
The following figure illustrates the structure of LINQ method
syntax.
Example
IList<Student> studentList = new List<Student>() {
new Student() { StudentID = 1, StudentName = "John", Age =
13} ,
new Student() { StudentID = 2, StudentName = "Moin", Age = 21 } ,
new Student() { StudentID = 3, StudentName = "Bill", Age = 18 } ,
new Student() { StudentID = 4, StudentName = "Ram" , Age =
20} ,
new Student() { StudentID = 5, StudentName = "Ron" , Age =
15 }
};
//
LINQ Method Syntax to find out teenager students
var teenAgerStudents = studentList.Where(s => s.Age > 12
&& s.Age < 20)
.ToList<Student>();
As you can see in the above figure, method syntax comprises
of extension methods and Lambda expression. The extension methods Where and ToList are defined in the Enumerable class.
