LINQ
1) What is LINQ?
LINQ is an Acronym of Language Integrated Query thave have a
uniform query syntax to query from different-2 Data Source like DataTable,
DataSet , XML Docs etc and you can write queries in C# and VB.Net.
LINQ provides a single
or uniform interface to query from Data sources.
2) How many types , we can query by LINQ?
There
are two types as below
·
Query Syntax or Query
Expression Syntax
var data= from a in Customers where a.ID > 10
Select a;
·
Method Syntax or Method
Extension Syntax
var data = Customers.Where(a=>a.ID > 10);
3) What is Anonymous function?
·
Anonymous function are
the special type of function that doesn’t have name
4) What are the query operator that can use in query?
There
are various operator provided by LINQ as given below
Below
are the list through which we can easily understand this concept
IList<Student>
lstStudent = new List<Student>{
new
Student(){ Name="A1",Email="ajay@gmail.com",Address="Delhi",Age=10 },
new
Student(){ Name="A2",Email="majay@gmai1l.com",Address="Saharanpur",Age=12 },
new Student(){ Name="A1",Email="ajay@gmail112.com",Address="Delhi",Age=14 },
new Student(){ Name="A5",Email="ajay@gmai2l.com",Address="Saharanpur" ,Age=28},
new Student(){ Name="A5",Email="ajay@gmai2l.com",Address="Noida" ,Age=30},
new
Student(){ Name="A3",Email="ajay@gmai2l.com",Address="NCR" ,Age=20}
};
This
is a list of students which have Name, Email and Address.
Where – this
operator is used to filter query data as you can use as follows
By Query Syntax
var
whereByQuery = from a in lstStudent
where a.Age > 10
select a;
By Method Syntax
var whereByMethod
= lstStudent.Where(a => a.Age > 10).ToList();
Orderby – orderby operator is used to sort
a list by ascending or descending
By Query Syntax
var
orderby = from a in lstStudent
orderby a.Address
select a;
var
orderbyDesc = from a in lstStudent
orderby a.Address
descending
select a;
By Method Syntax
var
orderbyMethod = lstStudent.OrderBy(a => a.Age).ToList();
var
orderbyMethodDesc = lstStudent.OrderByDescending(a => a.Age).ToList();
GroupBy – group by clause is used to get grouped record on the basis
of keys
By Query Syntax
var groupby = (from a in lstStudent group a by
a.Name).ToList();
By Method Syntax
var groupbyMethod =
(lstStudent.GroupBy(a=>a.Name)).ToList();
Join –
join operator is used to get unique values from both lists on key basis
By Query Syntax
var joina = (from a in lstStudent
join
m in lstCustomer
on a.Name equals m.Name
select new {
a.Name,
a.Age
}).ToList();
By Method Syntax
var joinViaMethod = lstStudent.Join( // OuterSequence
lstCustomer, //Inner Sequence
student =>
student.Name, //OuterKey
customer =>
customer.Name,//InnerKey
(student,
customer) => new {
Name=
student.Name,
age=
student.Age
}).ToList();
Sum --
To get Sum value for Numeric Item
By Query
Syntax
var sum = (from a in lstStudent
select a.Age).Sum();
By Method Syntax
var sumMethod = lstStudent.Sum(a=>a.Age);
Max -To
get Maximum value for Numeric Item
By Query Syntax
var max= (from a in lstStudent
select a.Age).Max();
By Method Syntax
var maxMethod = lstStudent.Max(a => a.Age);
Average
By Query Syntax
var avg = (from a in lstStudent
select a.Age).Average();
By Method Syntax
var avgMethod = lstStudent.Average(a => a.Age);
Min -
To get Minimum value for Numeric Item
By Query Syntax
var min = (from a in lstStudent
select a.Age).Min();
By Method Syntax
var minMethod = lstStudent.Min(a => a.Age);
Skip & Take - Skip() methods skips
the number of elements from first element and returns the rest
Take() methods
returns the number of elements specified
By Query Syntax
var skip = lstStudent.Skip(2).ToList();
var
take = lstStudent.Take(2).ToList();
var ThirdHighestSal = (from a in lstStudent
orderby
a.Age descending
select
a.Age).Take(3).Skip(2);
let –
let operator is used as a intermediate to get som calculation or get data on
function basis
By Query Syntax
var withLetKeywork = from query in lstStudent
let
NameinLower = query.Name.ToLower()
where
NameinLower.StartsWith("a")
select
NameinLower;
By Method Syntax
Into –
It is used to continue query after select statement as well as group by
statement
By Query Syntax
var
groupByKeywork = from gp in lstStudent
select gp into studentLower
where studentLower.Name.Contains("A1")
select studentLower;
