How to use Program Structure in C#

       In this c# tutorial, you will learn about the complete program structure of c# with examples.

C# Program Structure

• C# supports program structure with six sections. Out of six, the Main section is mandatory.

1. DOCUMENTATION SECTION

• It is an optional
• Gives the complete information about program like name of the program, author name, date, version and other details, etc
• C# supports two comment statements like java

2. PREDEFINED NAMESPACE SECTION

• It is an optional
• It is used to load the predefined .NET libraries using “using” keyword
• It is used to create different types of applications, algorithms, tools & OS, etc
• Ex. System, System.IO, System.Net, etc

Using Keyword

• It is a reserved keyword in C#.NET
• It is mainly used to load the system namespaces in .NET programming
• It is just like a java import statement.

3. USER DEFINED NAMESPACE SECTION

• It is also an optional section. Here we can create our own namespace
• Namespace is a set of classes / interfaces
• It is a container
• It is just like java packages.

Interfaces and Classes 

4. INTERFACES 

• It has only declaration, no body (no definition)
• All the methods in the interfaces are public by default
• All the variables in the interfaces are const by default
• Interfaces are defined using interface (reserved word)
• It has no constructor.

NOTE

• If the subclass inherits the interface, then the sub class must implement the methods of interface, else it is considered as an interface type.

5. CLASSES

• Collection of variables and methods are grouped together into a single entity (called class) 
• Unlike java, c# class is internal by default
• All the variables, methods, properties in the classes are private by default
• Classes are defined using the reserved word class
• It supports constructors (parameter and parameterless).

6. MAIN() METHOD SECTION

• It is essential part in program
• It starts the program execution
• It is an important to note that, 1st letter of the Main() method in C# must be capitalized.
• Main() method can return only void and int types.

1. Main Returning Nothing

Example

2. Main Returning a Value

Example

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