Object instantiation with new in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Object instantiation with new

Class Definition

↓

Call new Keyword

↓

Allocate Memory for Object

↓

Call Constructor

↓

Return Object Reference

↓

Assign to Variable

↓

Use Object

This flow shows how using 'new' creates a new object: memory is allocated, constructor runs, and a reference is returned and stored.

Execution Sample

C Sharp (C#)

class Person {
  public string Name;
  public Person(string name) { Name = name; }
}

Person p = new Person("Alice");

This code creates a new Person object with the name "Alice" and stores it in variable p.

Execution Table

Step	Action	Evaluation	Result
1	Call new Person("Alice")	Allocates memory for Person	Memory allocated
2	Call Person constructor with name="Alice"	Sets Name field	Name = "Alice"
3	Return reference to new Person object	Reference created	Reference to Person object
4	Assign reference to variable p	p now points to new object	p = reference to Person("Alice")

💡 Object created and reference assigned to variable p

Variable Tracker

Variable	Start	After Step 4
p	null	Reference to Person object with Name="Alice"

Key Moments - 2 Insights

Why do we use the 'new' keyword to create an object?

The 'new' keyword tells the program to allocate memory and call the constructor to create a new object, as shown in steps 1 and 2 of the execution table.

What does the variable 'p' hold after instantiation?

Variable 'p' holds a reference (or address) to the new Person object, not the object itself, as shown in step 4.

Visual Quiz - 3 Questions

Look at the execution table, what happens at step 2?

A The constructor sets the Name field

B Memory is allocated for the object

C The reference is assigned to variable p

D The object is destroyed

💡 Hint

Check the 'Action' and 'Result' columns at step 2 in the execution table.

At which step does the variable 'p' get its value?

A Step 3

B Step 2

C Step 4

D Step 1

💡 Hint

Look for the step where the reference is assigned to 'p' in the execution table.

If we omit 'new' and write 'Person p = Person("Alice");', what would happen?

A The object is created normally

B Compilation error because 'new' is missing

C The variable 'p' holds null

D The constructor is called twice

💡 Hint

Remember that 'new' is required to create objects in C#, as shown in the concept flow.

Concept Snapshot

Object instantiation with new in C#:
- Use 'new ClassName(args)' to create an object.
- 'new' allocates memory and calls the constructor.
- The constructor initializes the object.
- The variable holds a reference to the object.
- Without 'new', object creation fails.

Full Transcript

This lesson shows how to create a new object in C# using the 'new' keyword. First, the program allocates memory for the object. Then, it calls the constructor to set up the object's data. After that, it returns a reference to the new object. Finally, this reference is stored in a variable. The variable does not hold the object itself but a pointer to it. Using 'new' is necessary to create objects; without it, the code will not compile.