C# Introduction - ProgramIdea

C# Introduction

C# is powerful object-oriented and type-safe programming language. C# pronounced as "C Sharp" that developed by Microsoft. In January 1999, Mr. Anders Hejlsberg builds a team to develop a new language that is called as COOL on that time, which stood as C-Like Object Oriented Language. Finally in July 2000 at Professional Developer Conference, Microsoft announced the language renamed as C#. That was inspired by the musical notation "sharp".

C# is similar to C++, Java and VB. Like C++, operator overloading, enumeration, pre-processor directives, pointers, function pointer (delegates). Like VB, its supports the concepts of properties. Like Java, C# does not allow multiple inheritances. But also, C# comes up with some new features such as reflections, attributes, remoting, thread, streams, Linq, dynamic and many more.


The identifier is representing a unique user defined name for variable, class, function, event or interface.

Rule of defining an identifier:

  • 1. The identifier can be a unique name in the specific region where it's defined.
  • 2. It can be an alphanumeric name and start with the underscore ( _ ) but not start with a numeric value.
  • 3. It cannot be a keyword. If you want to use a keyword as an identifier then use @ symbol at the prefix.
        For example, public is a keyword. So you can use like @public.
  • 4. Identifiers are case-sensitive, means "abc" and "ABC" both are different-different identifiers in C#.
  • 5. White-space not allowed between characters of an identifier.


Variable is a type of object or property or field that represent a data type object and can be store a specific value. In other words, a variable is holding a value and indicating that memory location.
C# is a type-safety language, so each variable is representing a specific type at compile time or run time.

In below example, we are defining a variable x that is holding integer value 10.

// <data type> <variable name>;
int x = 10; 
// Here x is a variable that holding value of 10

There are different different ways to declare the variable and assign the values.

// Rule of defining variable in c#:

// Option 1
int a; 

// Option 2
int a = 10; 

// Option 3
int a, b, c; 

// Option 4
int a = 10, b, c; 

// Option 5
int a = 10, b = 20, c = 50;


Expression is combination of operands and operator. An expression is a sequence of one or more operands and zero or more operators that can be evaluated to a single value, object, method or namespace. Expression can consist of a literal value, a method invocation, an operator and its operands or a simple string value.

// Operators and operands expression
int a = 10;
int b = ((a + 25) * (a - 5) * 120); 

// literal and simple name expression
int i = 5;
string abc = "ProgramIdea Tutorial";

// Method invocation expression


Keywords are predefined reserved identifiers that have a special meaning to the compiler. They cannot be used as identifier, if you want then use @ syntax at the prefix.

Types of keyword:

1. Reserved Keyword – That always have a reserved special meaning. You cannot use these keywords as an identifier in you programming. For example: public, private, base, new, null, out, return, if, foreach, void, abstract, interface etc.

2. Contextual Keyword – That has special meaning only in a limited program context and that can be used as identifier outside of context. For example get, set, var, value, from etc.


A statement can consist of a single line of code that ends with a semicolon, or series of single-line statements in a block. A statement can be a block of codes that enclosed in { } brackets or can be nested blocks.

Types of statement:

1. Selection statement
if, else, switch

2. Iteration statement
for, foreach, while, do-while

3. Jump statement
break, return, goto, continue

4. Exception statement
try, catch, finally, throw