The Linq projection operator is used to retrieve one or more from the tables. Its like select syntax of the standard SQL query. Select and Select many are two types of linq projection operators.
Linq projection operators
- Select many
- Select
Linq Select Operator
The select operator is used to retrieving data from the list or collection. Its same as SQL select query.
Syntax
var data = from s in user select u
Example:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LinqDemoes
{
class Program
{
static void Main(string[] args)
{
List<User> user = new List<User>()
{
new User() { UserId = 1, Name = "Faisal", Age = 21 },
new User() { UserId = 2, Name = "Irshad", Age = 18 },
new User() { UserId = 2, Name = "Bhavdip", Age = 28 },
new User() { UserId = 3, Name = "Kaushik", Age = 28 },
new User() { UserId = 4, Name = "Kirti", Age = 25 }
};
var data = from s in user
select new {
Name = s.Name,
ID = s.UserId,
Age = s.Age
};
foreach (var item in data)
{
Console.WriteLine("The User name is {0} ID is {1} Age is {2}", item.Name, item.ID, item.Age);
}
Console.ReadLine();
}
public class User
{
public int UserId { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
}
}
Here, we have select all the users from the list and store it in s variable and then created a new selection for the users
Output:
The User name is Faisal ID is 1 Age is 21 The User name is Irshad ID is 2 Age is 18 The User name is Bhavdip ID is 2 Age is 28 The User name is Kaushik ID is 3 Age is 28 The User name is Kirti ID is 4 Age is 25
Linq Select Many Operator
Select Many operator is used for selecting values from the collection of data of a collection of data i.e nested collection
Syntax
var data = user.SelectMany(m => m.Hobby);
Example:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LinqDemoes
{
class Program
{
static void Main(string[] args)
{
List<User> user = new List<User>()
{
new User() { UserId = 1, Name = "Faisal", Age = 21, Hobby = new List<string> { "Coding", "Driving" } },
new User() { UserId = 2, Name = "Irshad", Age = 18, Hobby = new List<string> { "Coding1", "Driving1" } },
new User() { UserId = 2, Name = "Bhavdip", Age = 28, Hobby = new List<string> { "Coding2", "Driving2" } },
new User() { UserId = 3, Name = "Kaushik", Age = 28, Hobby = new List<string> { "Coding3", "Driving3" } },
new User() { UserId = 4, Name = "Kirti", Age = 25, Hobby = new List<string> { "Coding4", "Driving4" } }
};
var data = user.SelectMany(m => m.Hobby);
foreach (var item in data)
{
Console.WriteLine(item);
}
Console.ReadLine();
}
public class User
{
public int UserId { get; set; }
public string Name { get; set; }
public int Age { get; set; }
public List<string> Hobby { get; set; }
}
}
}
As you can see the SelectMany had written all the array of string otherwise we have to use the loop for accessing multiple properties.
Output:
Coding Driving Coding1 Driving1 Coding2 Driving2 Coding3 Driving3 Coding4 Driving4
