Renan Martins

Posted on Sep 30

When I Went Blank in an Interview – and What I Learned About LINQ

#dotnet #csharp #linq #interview

Recently, I had a job interview where I was asked a very simple question:
“What is LINQ?”

Even though I know the answer, my mind just froze. For some reason, the only word that came to me was “link”.

After the interview, I laughed at myself — but it also inspired me to write this short article, not only to reinforce the concept for myself but also to help other beginners in .NET who might face the same question.

What is LINQ in .NET?

LINQ stands for Language Integrated Query.
It is a feature of C# and .NET that allows developers to query and manipulate data in a consistent and expressive way, directly inside the programming language.

Why is LINQ important?

Before LINQ, working with different data sources (lists, XML, databases, etc.) required completely different approaches.
LINQ simplifies this by providing a unified syntax to query data, making code easier to read, write, and maintain.

A Simple Example

Imagine you want to filter even numbers from a list.

Query syntax:

var numbers = new List<int> { 1, 2, 3, 4, 5, 6 };

// LINQ query syntax
var evens = from n in numbers
            where n % 2 == 0
            select n;

foreach (var e in evens)
{
    Console.WriteLine(e);
}

Method syntax (more common in real-world projects, and also my preference):

var evens = numbers.Where(n => n % 2 == 0);

More Usage Examples

LINQ is not just about filtering. Here are some other powerful operators you’ll use often:

Count

var count = numbers.Count(); // 6

Any

var hasEven = numbers.Any(n => n % 2 == 0); // true

Where

var odds = numbers.Where(n => n % 2 != 0); // 1, 3, 5

OrderBy / OrderByDescending

var ordered = numbers.OrderBy(n => n);     // 1, 2, 3, 4, 5, 6
var desc = numbers.OrderByDescending(n => n); // 6, 5, 4, 3, 2, 1

Select

var squares = numbers.Select(n => n * n); // 1, 4, 9, 16, 25, 36

Combining Operators

var result = numbers
    .Where(n => n % 2 == 0)
    .OrderBy(n => n)
    .Select(n => $"Even number: {n}");

foreach (var item in result)
{
    Console.WriteLine(item);
}

Where Can You Use LINQ?

LINQ can be used in many contexts:

In-memory collections (List, Array, etc.) → LINQ to Objects
Databases (via Entity Framework) → LINQ to Entities
XML files → LINQ to XML
And more

Upcoming Articles in This Series

This article is just the beginning! I’ll be publishing more deep dives into how LINQ works under the hood and how we can even build our own LINQ-like library. Stay tuned for:

When I Went Blank in an Interview – and What I Learned About LINQ
Understanding IEnumerable in C#: The Foundation of LINQ 🔜 (coming soon)
How Extension Methods Unlock LINQ’s Magic in C# 🔜 (coming soon)
C#’s Hidden Gem: How Yield Return Makes Iterators Simple🔜 (coming soon)
Unit Testing Our First LINQ-like Methods in C# 🔜 (coming soon)
Teaching My Team How to Build LINQ from Scratch 🔜 (coming soon)

Final Thoughts

LINQ is one of the most powerful features in C#. It makes data querying integrated, type-safe, and expressive.

So, if someone asks me again in an interview, I’ll have a much clearer answer ready — and hopefully no more blanks!

💡 Interview-ready answer:

LINQ (Language Integrated Query) is a feature in .NET that provides a consistent and type-safe way to query and manipulate data from different sources (collections, databases, XML) directly within C#.

✅ That’s all, folks!

💬 Let’s Connect

Have any questions, suggestions for improvement, or just want to share your thoughts?

Feel free to leave a comment here, or get in touch with me directly on LinkedIn — I’d love to connect!

DEV Community