Value types vs reference types mental model in C Sharp (C#) - Visual Side-by-Side Comparison

Concept Flow - Value types vs reference types mental model

Declare value type variable

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Store actual data in variable

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Assign value type to another variable

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Copy data to new variable

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Change new variable value

↓

Original variable unchanged

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Declare reference type variable

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Store reference (address) to object

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Assign reference type to another variable

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Copy reference (both point to same object)

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Change object via new variable

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Original variable sees changed object

Value types hold actual data copied on assignment; reference types hold a pointer to data, so assignments share the same object.

Execution Sample

C Sharp (C#)

int a = 5;
int b = a;
b = 10;

class Box { public int Value; }
Box x = new Box() { Value = 5 };
Box y = x;
y.Value = 10;

Shows how value types copy data and reference types share the same object.

Execution Table

Step	Variable	Value	Action	Effect
1	a	5	Declare a and assign 5	a holds 5
2	b	5	Assign b = a	b copies value 5
3	b	10	Set b = 10	b changes to 10, a unchanged
4	x	ref#1	Create Box object with Value=5, assign to x	x points to object with Value=5
5	y	ref#1	Assign y = x	y points to same object as x
6	y.Value	10	Set y.Value = 10	Object's Value changes to 10
7	x.Value	10	Check x.Value	x sees updated Value 10

💡 Execution ends after showing value and reference type behaviors.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 5	After Step 6	Final
a	undefined	5	5	5	5	5
b	undefined	5	10	10	10	10
x	undefined	undefined	undefined	ref#1	ref#1	ref#1
y	undefined	undefined	undefined	ref#1	ref#1	ref#1
Object.Value (x/y)	undefined	undefined	undefined	5	10	10

Key Moments - 3 Insights

Why does changing b not affect a?

Because b is a value type copy of a (see execution_table step 3), changing b only changes its own copy.

Why does changing y.Value also change x.Value?

Because x and y both reference the same object (see execution_table step 5), so changing the object via y affects what x sees.

Is the data stored inside the variable for reference types?

No, the variable stores a reference (address) to the object, not the actual data (see execution_table step 4).

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the value of variable a?

A 5

B 10

C undefined

D ref#1

💡 Hint

Check variable 'a' value in execution_table row for step 3.

At which step do variables x and y start pointing to the same object?

A Step 2

B Step 4

C Step 5

D Step 6

💡 Hint

Look at the action and effect columns in execution_table rows for steps 4 and 5.

If we changed y.Value to 20 instead of 10 at step 6, what would x.Value be after?

A 5

B 20

C 10

D undefined

💡 Hint

Since x and y reference the same object, changing y.Value changes x.Value (see variable_tracker).

Concept Snapshot

Value types store actual data; copying duplicates data.
Reference types store address to data; copying duplicates reference.
Changing a copied value type does not affect original.
Changing data via one reference affects all references.
Examples: int is value type; class instances are reference types.

Full Transcript

This visual execution shows how value types and reference types behave differently in C#. Value types like int store the actual data in the variable. When you assign one value type variable to another, it copies the data. Changing the new variable does not affect the original. Reference types like class instances store a reference (address) to the object. Assigning one reference variable to another copies the reference, so both variables point to the same object. Changing the object through one variable is seen by the other. The execution table traces these steps with variables a, b (value types) and x, y (reference types). The variable tracker shows how values change after each step. Key moments clarify common confusions about copying and shared data. The quiz tests understanding of these behaviors. This mental model helps beginners grasp how data is stored and shared in C#.