Static members vs instance members in C Sharp (C#) - Visual Side-by-Side Comparison

Concept Flow - Static members vs instance members

Start

↓

Create Class

↓

Define Static Member

↓

Define Instance Member

↓

Create Object Instance

↓

Access Instance Member via Object

↓

Access Static Member via Class

↓

Use Members

↓

End

This flow shows how static members belong to the class itself and instance members belong to each object created from the class.

Execution Sample

C Sharp (C#)

class Car {
  public static int wheels = 4;
  public string color;

  public Car(string c) {
    color = c;
  }
}

Car car1 = new Car("red");
Console.WriteLine(Car.wheels);
Console.WriteLine(car1.color);

This code defines a class with a static member and an instance member, creates an object, and accesses both members.

Execution Table

Step	Action	Evaluation	Result
1	Define class Car with static wheels=4 and instance color	Class ready	Static wheels=4, no instances yet
2	Create car1 = new Car("red")	Constructor sets color	car1.color = "red"
3	Access Car.wheels	Static member accessed via class	Output: 4
4	Access car1.color	Instance member accessed via object	Output: red
5	End of execution	All members accessed	Program ends

💡 Program ends after accessing static and instance members

Variable Tracker

Variable	Start	After Step 2	Final
Car.wheels	4	4	4
car1.color	undefined	red	red

Key Moments - 2 Insights

Why do we access 'wheels' using the class name but 'color' using the object name?

Because 'wheels' is static and belongs to the class itself, so we use the class name (see step 3). 'color' is an instance member, so it belongs to each object and we access it via the object (see step 4).

Can we access instance members without creating an object?

No, instance members need an object to exist. Without creating 'car1', 'color' has no value (see step 2).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of Car.wheels at step 3?

A red

B undefined

C 4

D 0

💡 Hint

Check the 'Result' column at step 3 in the execution_table.

At which step is the instance member 'color' assigned a value?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' and 'Result' columns for when car1.color is set.

If we try to access 'color' using the class name like Car.color, what would happen?

A It will cause a compile-time error

B It will output the color value

C It will output null

D It will output 4

💡 Hint

Instance members require an object; see key_moments about access rules.

Concept Snapshot

Static members belong to the class and are shared by all instances.
Instance members belong to each object separately.
Access static members via ClassName.member.
Access instance members via object.member.
Static members exist even if no objects are created.
Instance members require an object to exist.

Full Transcript

This example shows a class Car with a static member wheels and an instance member color. The static member wheels is shared by all cars and accessed using the class name. The instance member color is unique to each car object and accessed through the object. We create car1 with color 'red'. Accessing Car.wheels gives 4, and car1.color gives 'red'. Static members do not need an object, but instance members do. Trying to access instance members without an object causes errors.