OrderBy and sorting in C Sharp (C#) - Step-by-Step Execution

Concept Flow - OrderBy and sorting

Start with collection

↓

Choose key to sort by

↓

Compare elements by key

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Rearrange elements in order

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Return sorted collection

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End

The program takes a collection, selects a key to sort by, compares elements, rearranges them, and returns the sorted collection.

Execution Sample

C Sharp (C#)

var numbers = new List<int> { 5, 3, 8, 1 };
var sorted = numbers.OrderBy(n => n);
foreach(var num in sorted) Console.Write(num + " ");

Sorts a list of numbers in ascending order and prints them.

Execution Table

Step	Action	Collection State	Output
1	Start with numbers list	[5, 3, 8, 1]
2	Apply OrderBy with key = number itself	[5, 3, 8, 1]
3	Compare elements and sort	[1, 3, 5, 8]
4	Iterate sorted collection	[1, 3, 5, 8]	1 3 5 8
5	End	[1, 3, 5, 8]	1 3 5 8

💡 All elements sorted ascending, iteration complete.

Variable Tracker

Variable	Start	After OrderBy	After Iteration	Final
numbers	[5, 3, 8, 1]	[5, 3, 8, 1]	[5, 3, 8, 1]	[5, 3, 8, 1]
sorted	null	[1, 3, 5, 8]	[1, 3, 5, 8]	[1, 3, 5, 8]
num	null	null	1, 3, 5, 8	8

Key Moments - 2 Insights

Why does the original list 'numbers' not change after OrderBy?

OrderBy returns a new sorted sequence without modifying the original list, as shown in execution_table rows 2 and 3 where 'numbers' stays the same but 'sorted' changes.

What does the lambda 'n => n' mean in OrderBy?

It means we sort by the number itself. The lambda picks each element as the key to sort by, as seen in execution_table step 2.

Visual Quiz - 3 Questions

Look at the execution_table, what is the collection state after sorting is applied?

A [8, 5, 3, 1]

B [5, 3, 8, 1]

C [1, 3, 5, 8]

D []

💡 Hint

Check execution_table row 3 under 'Collection State' to see the sorted list.

At which step does the program output the sorted numbers?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look at execution_table row 4 where 'Output' shows the printed numbers.

If we changed the lambda to 'n => -n', how would the sorted collection look?

A [8, 5, 3, 1]

B [1, 3, 5, 8]

C [5, 3, 8, 1]

D []

💡 Hint

Sorting by negative values reverses order; check how keys affect sorting in execution_table step 2.

Concept Snapshot

OrderBy sorts a collection by a key selector.
Syntax: collection.OrderBy(x => key)
Returns a new sorted sequence, original unchanged.
Sorts ascending by default.
Use lambda to pick sort key.
Iterate to see sorted results.

Full Transcript

This example shows how OrderBy sorts a list of numbers. We start with the list [5, 3, 8, 1]. OrderBy uses a lambda 'n => n' to sort by the number itself. It returns a new sorted sequence [1, 3, 5, 8] without changing the original list. Then we print each number in order. The key points are that OrderBy does not modify the original collection and that the lambda defines the sorting key.