Interface declaration syntax in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Interface declaration syntax

Start

↓

Write 'interface' keyword

↓

Name the interface

↓

Open curly brace '{'

↓

Declare method/property signatures

↓

Close curly brace '}'

↓

Interface ready to use

This flow shows how to write an interface: start with the keyword, name it, add method signatures inside braces, then finish.

Execution Sample

C Sharp (C#)

interface IAnimal
{
    void Speak();
    int Legs { get; }
}

Declares an interface named IAnimal with a method Speak and a read-only property Legs.

Execution Table

Step	Code Line	Action	Result
1	interface IAnimal	Declare interface named IAnimal	Interface IAnimal created
2	{	Open interface body	Ready to add members
3	void Speak();	Declare method signature Speak	Method Speak added to interface
4	int Legs { get; }	Declare read-only property Legs	Property Legs added to interface
5	}	Close interface body	Interface declaration complete

💡 Interface IAnimal declared with method Speak and property Legs signatures

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 4	Final
IAnimal	undefined	Declared as interface	Has method Speak()	Has property Legs { get; }	Complete interface

Key Moments - 2 Insights

Why don't we provide method bodies inside the interface?

Interfaces only declare what methods/properties must exist, not how they work. See execution_table step 3 where only the signature is declared without a body.

Can properties in interfaces have setters?

Yes, but in this example (step 4) Legs has only a getter. You can add a setter by writing { get; set; }.

Visual Quiz - 3 Questions

Look at the execution_table, what is declared at step 3?

A A property Legs

B A method signature Speak()

C The interface name

D The interface body closes

💡 Hint

Check the 'Code Line' and 'Action' columns at step 3 in execution_table

At which step does the interface declaration finish?

A Step 2

B Step 3

C Step 5

D Step 4

💡 Hint

Look for the step where the interface body closes in execution_table

If we add a setter to Legs property, which step changes?

A Step 4

B Step 3

C Step 1

D Step 5

💡 Hint

Property declarations happen at step 4 in execution_table

Concept Snapshot

Interface declaration syntax in C#:
interface InterfaceName
{
    ReturnType MethodName();
    PropertyType PropertyName { get; set; }
}
Interfaces declare method/property signatures without bodies.

Full Transcript

This visual trace shows how to declare an interface in C#. First, write the keyword 'interface' followed by the interface name. Then open curly braces to start the body. Inside, declare method signatures like 'void Speak();' without bodies, and properties like 'int Legs { get; }' with accessors but no implementation. Finally, close the braces to complete the interface. Interfaces only specify what methods and properties a class must have, not how they work. This example declares an interface named IAnimal with a Speak method and a read-only Legs property.