C# Program to Find the List of Students whose Name Starts with ‘S’ using where() Method of List Collection using LINQ

LINQ is known as Language Integrated Query and it is introduced in .NET 3.5. It gives the ability to .NET languages to generate queries to retrieve data from the data source. It removes the mismatch between programming languages and databases and the syntax used to create a query is the same no matter which type of data source is used. In this article, we will learn how to print the list of students whose name starts with ‘S’ using where() Method of List Collection. Here the where method filters the given sequence or array of values based on the predicate. To use the where() method you need to import System.Linq and System.Collections.Generic namespaces in your program.

Syntax:

Where<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>)

Example:

Input : List of Students:
        {{id = 101, name = "Sravan", age = 12},
         {id = 102, name = "deepu",  age = 15},
         {id = 103, name = "manoja", age = 13},
         {id = 104, name = "Sathwik", age = 12},
         {id = 105, name = "Saran",  age = 15}}
Output: {{id = 105, name = "sravan", age = 15},
         {id = 104, name = "Sathwik",age = 12},
         {id = 105, name = "Saran",  age = 15}}
     
Input: List of Students:
       {{id = 102, name = "deepu",  age = 15},
        {id = 103, name = "manoja", age = 13}}
Output: No Output

Approach:

To find the list of students whose name starts with ‘S’ follow the following steps:

1. Create a list of students with three variables(Id, name and age).
2. Iterate through the student details by using Where() function and get the student details by choosing student name starts with’ S’ using s => s.name[0] == ‘S’.
3. Now call the ToString() method.
4. Display the student details.

Example:

C#

// C# program to display the list of students whose
// name starts with 'S'. Using Where() function
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Student{

// Declare 3 variables - id, age and name
int id;
int age;
string name;

// Get the to string method that returns
// id , name and age
public override string ToString()
{
    return id + " " + name + " " + age;
}

// Driver code
static void Main(string[] args)
{

    // Declare a list variable
    List<Student> student = new List<Student>()
    {

        // Create 5 Student details
        new Student{ id = 101, name = "Sravan", age = 12  },
        new Student{ id = 102, name = "deepu", age = 15 },
        new Student{ id = 103, name = "manoja", age = 13 },
        new Student{ id = 104, name = "Sathwik", age = 12 },
        new Student{ id = 105, name = "Saran", age = 15 }

    };

    // Iterate the Student by selecting Student
    // name starts with S
    // Using Where() function
    IEnumerable<Student> Query = student.Where(s => s.name[0] == 'S');

    // Display employee details
    Console.WriteLine("ID  Name  Age");
    Console.WriteLine("+++++++++++++");
    foreach (Student e in Query)
    {

        // Call the to string method
        Console.WriteLine(e.ToString());
    }
}
}

Output:

ID  Name  Age
+++++++++++++
101 Sravan 12
104 Sathwik 12
105 Saran 15