Struct declaration and behavior in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Struct declaration and behavior

Declare struct type

↓

Create struct variable

↓

Assign values to fields

↓

Use struct variable

↓

Copy struct variable?

Yes↓

Create independent copy

↓

Modify copy does NOT affect original

↓

End

This flow shows how a struct is declared, used, and how copying creates independent values.

Execution Sample

C Sharp (C#)

struct Point {
  public int X;
  public int Y;
}

Point p1 = new Point { X = 1, Y = 2 };
Point p2 = p1;
p2.X = 5;

This code declares a struct Point, creates one instance, copies it, and changes the copy's field.

Execution Table

Step	Action	Variable States	Notes
1	Declare struct Point with fields X and Y	No variables yet	Struct type created
2	Create p1 with X=1, Y=2	p1: {X=1, Y=2}	p1 holds values 1 and 2
3	Copy p1 to p2	p1: {X=1, Y=2}, p2: {X=1, Y=2}	p2 is a separate copy of p1
4	Change p2.X to 5	p1: {X=1, Y=2}, p2: {X=5, Y=2}	p2 changed, p1 unchanged
5	End	p1: {X=1, Y=2}, p2: {X=5, Y=2}	Struct copy is independent

💡 Execution ends after modifying p2; p1 remains unchanged because structs are value types.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
p1	undefined	{X=1, Y=2}	{X=1, Y=2}	{X=1, Y=2}	{X=1, Y=2}
p2	undefined	undefined	{X=1, Y=2}	{X=5, Y=2}	{X=5, Y=2}

Key Moments - 3 Insights

Why does changing p2.X not affect p1.X?

Because structs are value types, copying p1 to p2 creates a new independent copy. See execution_table step 4 where p2.X changes but p1.X stays the same.

Is the struct variable a reference or a value?

Struct variables hold values directly, not references. This is why copying creates independent copies, as shown in execution_table step 3.

What happens if we assign one struct variable to another?

A full copy of the struct's data is made. Both variables then hold separate copies, so changes to one do not affect the other (execution_table step 3 and 4).

Visual Quiz - 3 Questions

Look at the execution_table at step 4, what is the value of p1.X?

A 0

B 5

C 1

D Undefined

💡 Hint

Check the Variable States column at step 4 in execution_table.

At which step does p2 get its own copy of p1's data?

A Step 3

B Step 2

C Step 4

D Step 1

💡 Hint

Look for the step where p2 is assigned values from p1 in execution_table.

If structs were reference types, what would happen when p2.X changes?

A p1.X would stay the same

B p1.X would also change

C p2.X would revert to p1.X

D Compilation error

💡 Hint

Think about how reference types share the same data, unlike value types shown in variable_tracker.

Concept Snapshot

struct StructName {
  public Type Field1;
  public Type Field2;
}

- Structs are value types.
- Assigning copies all data.
- Changes to copies do not affect originals.

Full Transcript

This visual trace shows how a struct is declared and used in C#. First, the struct type Point is declared with two integer fields X and Y. Then, a variable p1 of type Point is created and initialized with X=1 and Y=2. Next, p1 is copied to p2, creating an independent copy. When p2.X is changed to 5, p1.X remains 1, showing that structs hold values directly and copying creates separate instances. This behavior is different from reference types where variables share the same data. The key moments highlight why changes to copies do not affect originals and clarify that structs are value types. The quiz questions reinforce understanding of when copies happen and how values change during execution.