How to Use LINQ in C#: Simple Syntax and Examples

LINQ in C# lets you query collections using from, where, and select keywords in a readable way. You write queries like SQL but directly in C# to filter, sort, or transform data easily.

Syntax

LINQ queries use a simple pattern with these parts:

• from: defines the data source and a variable for each item
• where: filters items based on a condition
• select: chooses what to return from each item

This pattern reads like a sentence and works on arrays, lists, or any collection.

csharp

var result = from item in collection
             where item.Property > 10
             select item;

Example

This example shows how to use LINQ to find even numbers from a list and print them.

csharp

using System;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6 };

        var evenNumbers = from num in numbers
                          where num % 2 == 0
                          select num;

        foreach (var n in evenNumbers)
        {
            Console.WriteLine(n);
        }
    }
}

Output

2
4
6

Common Pitfalls

Common mistakes when using LINQ include:

• Forgetting to include using System.Linq; which is required for LINQ methods.
• Confusing query syntax with method syntax (both work but have different forms).
• Not realizing LINQ queries are lazy and only run when you iterate or convert to a list.

Here is a wrong and right way to use LINQ:

csharp

// Wrong: Missing using directive
// var evens = numbers.Where(n => n % 2 == 0); // Error if System.Linq not included

// Right:
using System.Linq;
var evens = numbers.Where(n => n % 2 == 0);

Quick Reference

LINQ Keyword/Method	Purpose
from	Start query and define data source
where	Filter items by condition
select	Choose what to return
OrderBy	Sort items ascending
OrderByDescending	Sort items descending
GroupBy	Group items by key
Join	Combine two collections
ToList	Convert query result to list
FirstOrDefault	Get first item or default if none

Key Takeaways

LINQ lets you write readable queries directly in C# to work with collections.

Use from, where, and select keywords to build queries.

Always include using System.Linq; to access LINQ features.

LINQ queries run only when you iterate or convert them, so they are lazy by default.

You can use both query syntax and method syntax depending on your preference.