Computed properties in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Computed properties

Define class with computed property

↓

Create object instance

↓

Access computed property

↓

Run get accessor code

↓

Return computed value

↓

Use value in program

The flow shows how a computed property is defined, accessed, and returns a value calculated on the fly.

Execution Sample

C Sharp (C#)

class Rectangle {
  public int Width { get; set; }
  public int Height { get; set; }
  public int Area => Width * Height;
}

var rect = new Rectangle { Width = 3, Height = 4 };
Console.WriteLine(rect.Area);

This code defines a Rectangle with Width and Height, and a computed property Area that multiplies them. It prints the area.

Execution Table

Step	Action	Variable/Property	Value	Explanation
1	Create Rectangle object	rect	Rectangle instance	Object with Width and Height properties created
2	Set Width	rect.Width	3	Width property set to 3
3	Set Height	rect.Height	4	Height property set to 4
4	Access computed property Area	rect.Area	12	Area getter runs: 3 * 4 = 12
5	Print Area	Output	12	Area value 12 printed to console

💡 All steps complete, program ends after printing computed Area

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
rect.Width	0 (default)	3	3	3	3
rect.Height	0 (default)	0	4	4	4
rect.Area	N/A	N/A	N/A	12	12

Key Moments - 2 Insights

Why does rect.Area not store a value but still returns 12?

Because Area is a computed property with only a get accessor that calculates Width * Height each time it is accessed, it does not store a value but computes it on demand (see execution_table step 4).

What happens if Width or Height changes after accessing Area once?

Area will reflect the new product because it computes the value every time it is accessed, not just once (not shown here but implied by the computed property behavior).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of rect.Area at step 4?

A 0

B 7

C 12

D Undefined

💡 Hint

Check the 'Value' column for step 4 in execution_table where Area is accessed.

At which step is rect.Height set to 4?

A Step 3

B Step 4

C Step 2

D Step 5

💡 Hint

Look at the 'Action' and 'Variable/Property' columns in execution_table.

If rect.Width was changed to 5 after step 3, what would rect.Area be at step 4?

A 12

B 20

C 7

D 9

💡 Hint

Area computes Width * Height each time; changing Width to 5 and Height is 4 means 5*4=20.

Concept Snapshot

Computed properties in C# use get accessors to calculate values on demand.
Syntax: public int PropertyName => expression;
They do not store values but compute each time accessed.
Useful for values derived from other properties.
Example: Area => Width * Height.

Full Transcript

This example shows a Rectangle class with Width and Height properties and a computed property Area that multiplies them. When we create a Rectangle object and set Width to 3 and Height to 4, accessing Area runs the get accessor which calculates 3 times 4 and returns 12. This value is printed. The computed property does not store the area but calculates it fresh each time it is accessed. This means if Width or Height changes later, Area will reflect the new product automatically.