LINQ query to get the number of rows selected

Introduction

In order to get the number of rows selected with LINQ, we use the Count method.

Count

The Count method allows you to count the number of elements in a list.

Examples

Simple usage

List<int> list = new List<int> { 55, 301, 14, 13, 1, 77, 17, 33};

int count = list.Count(); // 8

Usage in Conjunction with the Where method

List<int> list = new List<int> { 23, 18, 7, 91, 115, 102, 33, -88, 77, -6, 12};

int count = list.Where(l => l > 100).Count();  // 2

Advanced usage

Besides using primitive types with the Count method, we can also use reference types.

public class Student {

    public string FullName { get; set; }

    public int Age { get; set; }
}

List<Student> students = new List<Student> {
    new Student{ FullName = "Emilio Maxwell", Age = 23},
    new Student{ FullName = "Shannon Vaughn", Age = 14},
    new Student{ FullName = "Emilio Maxwell", Age = 17},
    new Student{ FullName = "Alma Cunningham", Age = 15},
    new Student{ FullName = "Gilberto Christensen", Age = 20},
    new Student{ FullName = "Emmett Banks", Age = 19},
    new Student{ FullName = "Robyn May", Age = 16},
    new Student{ FullName = "Candice Thompson", Age = 13}
}; 

/* Number of adult students */
int count = students.Where(l => l.Age > 18).Count(); // 3

Note: Instead of using the Where method, we can also specify our conditions inside the Count method and the result will be the same.

/* Number of adult students */
int count = students.Count(l => l.Age > 18); // 3

Namespace

To use the Count method, you have to include this namespace:

using System.Linq;