C# – LINQ Select Examples

Select is a LINQ functionality to define a data format of the query results.

Each of below examples is presented in C# with both Lambda and Query expression.

Let’s create a Person class.

public class Person
{
    public string Forename { get; set; }
    public string Surname { get; set; }
    public DateTime DateOfBirth { get; set; }
}

public class Person

{

public string Forename { get; set; }

public string Surname { get; set; }

public DateTime DateOfBirth { get; set; }

}

And collection of people which we query with LINQ expressions.

var people = new List<Person>()
{
    new Person()
    {
        Forename = "John", 
        Surname = "Smith", 
        DateOfBirth = new DateTime(1980, 6, 14)
    },
    new Person()
    {
        Forename = "Bob", 
        Surname = "Williams", 
        DateOfBirth = new DateTime(1974, 2, 21)
    },
    new Person()
    {
        Forename = "Chris", 
        Surname = "Jones", 
        DateOfBirth = new DateTime(1990, 10, 4)
    }
};

var people = new List<Person>()

{

new Person()

{

Forename = "John",

Surname = "Smith",

DateOfBirth = new DateTime(1980, 6, 14)

new Person()

{

Forename = "Bob",

Surname = "Williams",

DateOfBirth = new DateTime(1974, 2, 21)

new Person()

{

Forename = "Chris",

Surname = "Jones",

DateOfBirth = new DateTime(1990, 10, 4)

}

};

1. Select single value

Query collection to get forenames only.

Lambda expression:

var items = people.Select(x => x.Forename);

1	var items = people.Select(x => x.Forename);

Query expression:

var items = from p in people
            select p.Forename;

1 2	var items = from p in people select p.Forename;

Print to screen:

foreach (var item in items)
    Console.WriteLine(item);

1 2	foreach (var item in items) Console.WriteLine(item);

Result:

John
Bob
Chris

John

Bob

Chris

2. Select anonymous type

Query collection to get anonymous type objects containing surname and year of birth.

Lambda expression:

var items = people.Select(
    x => new
    {
        Surname = x.Surname,
        YearOfBirth = x.DateOfBirth.Year
    }
);

var items = people.Select(

x => new

{

Surname = x.Surname,

YearOfBirth = x.DateOfBirth.Year

}

);

Query expression:

var items = from p in people
            select new
            {
                Surname = p.Surname,
                YearOfBirth = p.DateOfBirth.Year 
            };

var items = from p in people

select new

{

Surname = p.Surname,

YearOfBirth = p.DateOfBirth.Year

};

Print to screen:

foreach (var item in items)
    Console.WriteLine(item.Surname + ", " + item.YearOfBirth);

1 2	foreach (var item in items) Console.WriteLine(item.Surname + ", " + item.YearOfBirth);

Result:

Smith, 1980
Williams, 1974
Jones, 1990

Smith, 1980

Williams, 1974

Jones, 1990

3. Select existing type

Query collection to get Person objects with upper-cased forenames and surnames.

Lambda expression:

var items = people.Select(
    x => new Person()
    {
        Forename = x.Forename.ToUpper(),
        Surname = x.Surname.ToUpper(),
        DateOfBirth = x.DateOfBirth
    }
);

var items = people.Select(

x => new Person()

{

Forename = x.Forename.ToUpper(),

Surname = x.Surname.ToUpper(),

DateOfBirth = x.DateOfBirth

}

);

Query expression:

var items = from p in people
            select new Person()
            {
                Forename = p.Forename.ToUpper(),
                Surname = p.Surname.ToUpper(),
                DateOfBirth = p.DateOfBirth
            };

var items = from p in people

select new Person()

{

Forename = p.Forename.ToUpper(),

Surname = p.Surname.ToUpper(),

DateOfBirth = p.DateOfBirth

};

Print to screen:

foreach (var item in items)
    Console.WriteLine(item.Forename + " " + item.Surname);

1 2	foreach (var item in items) Console.WriteLine(item.Forename + " " + item.Surname);

Result:

JOHN SMITH
BOB WILLIAMS
CHRIS JONES

JOHN SMITH

BOB WILLIAMS

CHRIS JONES