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C# Academy · Lesson

LINQ preview: Where, Select, OrderBy, Take/Skip; deferred execution

Build small LINQ pipelines over IEnumerable : filter with Where, transform with Select, order with OrderBy, and learn deferred execution vs materialization.

LINQ preview: Where, Select, OrderBy, Take/Skip; deferred execution is a free C# Academy lesson on CoddyKit — lesson 3 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C# Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.

LINQ overview

Goal: Use tiny LINQ pipelines to filter, transform, and order data.

  • Where (filter)
  • Select (map)
  • OrderBy, Take/Skip
  • Deferred execution & materialization

Where + Select

Chain Where (filter) then Select (transform). Read left-to-right.

using System;
using System.Linq;

public class Program
{
  public static void Main(string[] args)
  {
    int[] data = new int[] { 1, 2, 3, 4, 5, 6 };

    // Filter even numbers, then square them
    var query = data.Where(x => x % 2 == 0)
                    .Select(x => x * x);

    foreach (int n in query)
    {
      Console.WriteLine(n); // 4, 16, 36
    }
  }
}

OrderBy + Take

Sort with OrderBy (and ThenBy), limit with Take.

using System;
using System.Linq;

public class Program
{
  public static void Main(string[] args)
  {
    string[] names = new string[] { "Zoe", "Ada", "Alan", "Bob" };

    var top2 = names.OrderBy(s => s.Length) // shortest first
                    .ThenBy(s => s)         // tie-breaker
                    .Take(2);

    foreach (string s in top2)
    {
      Console.WriteLine(s); // Ada, Bob
    }
  }
}

Projection (anonymous type)

Select can create anonymous objects for quick shape changes (Word, Length).

using System;
using System.Linq;

public class Program
{
  public static void Main(string[] args)
  {
    string[] words = new string[] { "map", "filter", "reduce" };

    var info = words.Select(w => new { Word = w, Length = w.Length });

    foreach (var x in info)
    {
      Console.WriteLine(x.Word + " (" + x.Length + ")");
    }
  }
}

Deferred execution

Deferred: Query runs when you iterate. Changes to the source before enumeration affect results.

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

public class Program
{
  public static void Main(string[] args)
  {
    List<int> numbers = new List<int> { 1, 2, 3 };

    var q = numbers.Where(x => x > 1); // not executed yet

    numbers.Add(4); // modify source before enumeration

    foreach (int x in q) // executes here
    {
      Console.WriteLine(x); // 2, 3, 4
    }
  }
}

Materialize & syntax

Use ToList/ToArray to execute and store results. Query syntax is another way to write the same pipeline.

using System;
using System.Linq;

public class Program
{
  public static void Main(string[] args)
  {
    int[] data = new int[] { 3, 1, 2 };

    // Method syntax + materialize
    var sorted = data.OrderBy(x => x).ToList(); // executes now
    data[0] = 100; // will not affect 'sorted' (already materialized)

    foreach (int n in sorted) { Console.WriteLine(n); } // 1,2,3

    // Query syntax (equivalent)
    var query =
      from x in data
      where x < 50
      select x * 2;

    foreach (int n in query) { Console.WriteLine(n); } // 2,4
  }
}

Deferred execution meaning

Quick check: What does it mean that most LINQ operators are deferred?

Recap

Recap: Build pipelines with Where, Select, OrderBy, and Take/Skip. LINQ is deferred—materialize with ToList/ToArray when you need stable results.

Frequently asked questions

Is the “LINQ preview: Where, Select, OrderBy, Take/Skip; deferred execution” lesson free?

Yes — the full text of “LINQ preview: Where, Select, OrderBy, Take/Skip; deferred execution” is free to read here on the web, and the C# Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C# Academy course, upgrade to CoddyKit PRO.

What will I learn in “LINQ preview: Where, Select, OrderBy, Take/Skip; deferred execution”?

Build small LINQ pipelines over IEnumerable : filter with Where, transform with Select, order with OrderBy, and learn deferred execution vs materialization. You practise C# Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start C# Academy?

No prior experience is required. C# Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 3, so you can start here or from the beginning and move at your own pace.

How long does the “LINQ preview: Where, Select, OrderBy, Take/Skip; deferred execution” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this C# Academy lesson?

Yes. Every C# Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Arrays, slicing, List , Dictionary
  2. foreach patterns; collection initializers
  3. LINQ preview: Where, Select, OrderBy, Take/Skip; deferred execution
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