Reference assignment and shared state in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Reference assignment and shared state

Create Object A

↓

Assign Reference B = A

↓

Modify Object via B

↓

Check Object via A

↓

Both A and B see same changes

When you assign one reference variable to another, both point to the same object. Changes through one reference affect the shared object.

Execution Sample

C Sharp (C#)

class Box {
  public int Value;
}
Box a = new Box();
a.Value = 5;
Box b = a;
b.Value = 10;
Console.WriteLine(a.Value);

This code shows two references pointing to the same object; changing the object via one reference affects the other.

Execution Table

Step	Action	Variable States	Output
1	Create new Box object and assign to 'a'	a -> Box(Value=0)
2	Set a.Value = 5	a -> Box(Value=5)
3	Assign b = a (both reference same object)	a -> Box(Value=5), b -> Box(Value=5)
4	Set b.Value = 10 (modifies shared object)	a -> Box(Value=10), b -> Box(Value=10)
5	Print a.Value	a -> Box(Value=10), b -> Box(Value=10)	10

💡 Execution ends after printing the shared object's Value, which is 10.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
a	null	Box(Value=5)	Box(Value=5)	Box(Value=10)	Box(Value=10)
b	null	null	Box(Value=5)	Box(Value=10)	Box(Value=10)

Key Moments - 2 Insights

Why does changing b.Value also change a.Value?

Because both 'a' and 'b' reference the same Box object (see execution_table step 3 and 4). Changing the object through 'b' affects what 'a' sees.

Does assigning b = a create a new object?

No, it only copies the reference. Both variables point to the same object (execution_table step 3).

Visual Quiz - 3 Questions

Look at the execution_table at step 4, what is the value of a.Value?

A 10

B 5

C 0

D Undefined

💡 Hint

Check the Variable States column at step 4 where both a and b have Value=10.

At which step do 'a' and 'b' start referencing the same object?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

See the Variable States column; step 3 shows both a and b pointing to the same Box.

If we changed b.Value to 20 instead of 10 at step 4, what would a.Value be at the end?

A 5

B 20

C 10

D 0

💡 Hint

Since a and b share the same object, changing b.Value changes a.Value too (see variable_tracker).

Concept Snapshot

Reference assignment means two variables point to the same object.
Changing the object via one reference affects all references.
Assigning one reference to another copies the reference, not the object.
Use this to share and modify data without copying.
Remember: value types behave differently.

Full Transcript

This example shows how reference assignment works in C#. We create a Box object and assign it to variable 'a'. Then we assign 'b' to 'a', so both point to the same object. When we change the Value property through 'b', the change is visible through 'a' because they share the same object. The output prints 10, showing the shared state. This helps understand that reference variables hold addresses to objects, not copies.