Data Types

C# is a strongly typed language. It means, that you cannot use variable without data types. Data types tell the compiler that which type of data is used for processing. Such as if you want to work with string value then you will have to assign string type variable to work with.

The varibles in C#, are categorized into the following types:

1. Value types
2. Reference types
3. Pointer types
4. Value Type

Value type variables can be assigned a value directly. They are derived from the class System.ValueType.

The value types directly contain data. Some examples are int, char, and float, which stores numbers, alphabets, and floating point numbers, respectively. When you declare an int type, the system allocates memory to store the value.

To get the exact size of a type or a variable on a particular platform, you can use the sizeof method. The expression sizeof(type) yields the storage size of the object or type in bytes. Following is an example to get the size of int type on any machine:

using System;
namespace DataTypeApplication
{
   class Program
   {
      static void Main(string[] args)
      {
         Console.WriteLine("Size of int: {0}", sizeof(int));
         Console.ReadLine();
      }
   }
}
When the above code is compiled and executed, it produces the following result:

Size of int: 4
Reference Type

The reference types do not contain the actual data stored in a variable, but they contain a reference to the variables.

In other words, they refer to a memory location. Using multiple variables, the reference types can refer to a memory location. If the data in the memory location is changed by one of the variables, the other variable automatically reflects this change in value. Example of built-in reference types are: object,dynamic, and string.

Object Type

The Object Type is the ultimate base class for all data types in C# Common Type System (CTS). Object is an alias for System.Object class. The object types can be assigned values of any other types, value types, reference types, predefined or user-defined types. However, before assigning values, it needs type conversion.

When a value type is converted to object type, it is called boxing and on the other hand, when an object type is converted to a value type, it is calledunboxing.

object obj;
obj = 100; // this is boxing
Dynamic Type

You can store any type of value in the dynamic data type variable. Type checking for these types of variables takes place at run-time.

Syntax for declaring a dynamic type is:

dynamic <variable_name> = value;
For example,

dynamic d = 20;
Dynamic types are similar to object types except that type checking for object type variables takes place at compile time, whereas that for the dynamic type variables takes place at run time.

String Type

The String Type allows you to assign any string values to a variable. The string type is an alias for the System.String class. It is derived from object type. The value for a string type can be assigned using string literals in two forms: quoted and @quoted.

For example,

String str = "Tutorials";
A @quoted string literal looks as follows:

@"Tutorials";
The user-defined reference types are: class, interface, or delegate. We will discuss these types in later chapter.

Pointer Type

Pointer type variables store the memory address of another type. Pointers in C# have the same capabilities as the pointers in C or C++.

Syntax for declaring a pointer type is:

type* identifier;
For example,

char* cptr;
int* iptr;

Boxing and Unboxing

Boxing: Implicit conversion of a value type (int, char etc.) to a reference type (object), is known as Boxing. In boxing process, a value type is being allocated on the heap rather than the stack.

1.          It converts a value type into a reference type.
2.          Values are stored in the Stack first then moved to the heap.
3.          Creates a container/box for holding the value.

C# - Generics

Generics are the most powerful feature of C# 2.0. Generics allow you to define type-safe data structures, without committing to actual data types. This results in a significant performance boost and higher quality code, because you get to reuse data processing algorithms without duplicating type-specific code. 

Generics provide a facility for creating data structures that are specialized to handle specific types when declaring a variable. Programmers define these parameterized types so that each variable of a particular generic type has the same internal algorithm but the types of data and method signatures can vary based on programmer preference.

C# - Casting & Type Conversion

Type conversion is converting one type of data to another type. It is also known as Type Casting. In C#, type casting has two forms:

Implicit type conversion – These conversions are performed by C# in a type-safe manner. For example, are conversions from smaller to larger integral types and conversions from derived classes to base classes.(সফটওয়ারের দায়িত্তে)
Explicit type conversion – These conversions are done explicitly by users using the pre-defined functions. Explicit conversions require a cast operator.(নিজের দায়িত্তে)

C# - Attribute

Attribute is nothing more than a class that inherit from the base class Attribute.

C# - Operator Overloading

In an object oriented programming language like C#, operator overloading provides a much more natural way of implementing the operations on custom types.Suppose that we have a class created for Complex number and we want to perform all the arithmetic operations on this type. One way to do this is by having functions like Add, Subtract inside the class and have the functionality. Another way is to actually have the overloaded version of operators to act on this type.

C# - Interface

What an interface is?

In the real world, an interface means a medium to interact with something. To be precise, it's a point where two systems, subjects, organizations and so on meet and interact. There are a few rules for the interaction to be done. Suppose you are going for an interview of Programmer Profile. The interview is only possible if the interviewer and you speak the same language. Moreover, you and the interviewer have the same skill set of programming languages to discuss upon.