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C# Academy · Lesson

Select and Projection

Shape data into new forms.

What Projection Means

Select transforms each element of a sequence into a new shape. This is called projection.

It takes a lambda that maps one element to a result, and returns a sequence of those results — leaving the source untouched.

using System;
using System.Linq;

int[] nums = { 1, 2, 3, 4 };
var squares = nums.Select(n => n * n);
Console.WriteLine(string.Join(", ", squares));

Changing the Type

Projection can change the element type entirely. Mapping int to string produces an IEnumerable<string>.

The output type is inferred from the lambda's return type, so the compiler tracks it for you.

using System;
using System.Linq;

int[] nums = { 10, 20, 30 };
var labels = nums.Select(n => $"Item #{n}");
foreach (var l in labels) Console.WriteLine(l);

All lessons in this course

  1. Where and Filtering
  2. Select and Projection
  3. OrderBy and Grouping
  4. Aggregates and ToList
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