1.4. C# basic syntax

C# is an object-oriented programming language. In the object-oriented programming method, the program consists of a variety of objects that interact with each other. Objects of the same kind usually have the same type, that is to say, in the same class medium.

For example, take a Rectangle object as an example. It has length and width Property. Depending on the design, it may need to accept these property values, calculate the area, and display details.

Let’s look at the implementation of a Rectangle class and discuss basic syntax of C# :

1.4.1. Example #

using System;
namespace RectangleApplication
{
    class Rectangle
    {
        // Member variables
        double length;
        double width;
        public void Acceptdetails()
        {
            length = 4.5;
            width = 3.5;
        }
        public double GetArea()
        {
            return length * width;
        }
        public void Display()
        {
            Console.WriteLine("Length: {0}", length);
            Console.WriteLine("Width: {0}", width);
            Console.WriteLine("Area: {0}", GetArea());
        }
    }

    class ExecuteRectangle
    {
        static void Main(string[] args)
        {
            Rectangle r = new Rectangle();
            r.Acceptdetails();
            r.Display();
            Console.ReadLine();
        }
    }
}

When the above code is compiled and executed, it produces the following results:

Length: 4.5
Width: 3.5
Area: 15.75

using Keyword #

The first statement in any C# program is:

using System;

using keyword is used to include namespaces in the program. A program can contain multiple using statement.

`class` keyword #

class keyword is used to declare a class

C# Comments #

Comments are used to interpret code. The compiler ignores annotated entries.In a C# program, multiple lines are commented to /* start with a character */ to terminate, as follows:

/* This program demonstrates
The basic syntax of C# programming
Language */

Single-line comments are made with // . For example:

} //end class Rectangle

Member variable #

Variables are properties or data members of a class that are used to store data. In the above program Rectangle class has two member variables named length and width .

Member function #

A function is a series of statements that perform a specified task. The member functions of a class are declared within the class. Our example classRectangle contains three member functions: AcceptDetails 、 GetArea and Display .

Instantiate a class #

In the above program, the class ExecuteRectangle is a containing Main() methods and instancing Rectangle class.

Identifier #

Identifiers are used to identify classes, variables, functions, or any other user-defined item. In C#, class naming must follow the following basic rules:

Identifiers must be alphabetic, underscore, or @ , the beginning can be followed by a series of letters, numbers (0-9), an underscore ( _ ), @ .
The first character in an identifier cannot be a number.
Identifiers must not contain any embedded spaces or symbols, such as ? - +! # % ^ & * ( ) [ ] { } . ; : " ' / \ .
The identifier cannot be a C# keyword. Unless they have one @ prefix. For example, @if is a valid identifier, but if is not, because if is a keyword.
Identifiers must be case sensitive. Uppercase and lowercase letters are considered different letters.
Cannot be the same as the class library name of C#.

C# keyword #

Keywords are reserved words predefined by the C# compiler. These keywords cannot be used as identifiers, but if you want to use these keywords as identifiers, you can add @ characters as prefixes.

In C#, some keywords have a special meaning in the context of the code, such as get and set , which are called context keywords (contextual keywords)

The following table lists the reserved keywords and context keywords in C#:

Reserved keyword #
Abstract	As	Base	Bool	Break	Byte	Case
Catch	Char	Checked	Class	Const	Continue	Decimal
Default	Delegate	Do	Double	Else	Enum	Event
Explicit	Extern	FALSE	Finally	Fixed	Float	For
Foreach	Goto	If	Implicit	In	In (generic modifier)	Int
Interface	Internal	Is	Lock	Long	Namespace	New
Null	Object	Operator	Out	Out (generic modifier)	Override	Params
Private	Protected	Public	readonly	Ref	Return	Sbyte
Sealed	Short	Sizeof	Stackalloc	Static	string	Struct
switch	This	Throw	TRUE	Try	typeof	Uint
Ulong	Unchecked	Unsafe	Ushort	Using	virtual	Void
Volatile	While

Context keyword #
Add	Alias	Ascending	Descending	Dynamic	From	Get
Global	Group	Into	Join	let	Orderby	Partial (type)
Partial	Remove	Select	Set
(method)