As we know that C# is strongly typed computer language so we must declare the type of a variable that indicates the kind of values it is going to store eg. integer, float, string etc.

string stringVar = "Hello DotNet Palace!!";
int intVar = 10;
float floatVar = 20.2f;
char charVar = 'D';
bool boolVar = true;
 

Kinds of datatypes in C#

C# supports two kinds of data types: Value types and Reference types.

Value types

A data type is a value type if it holds a data value within its own memory space. It means the variables of these data types directly contain values. C# supports below kinds of datatypes of value type:

• bool
• byte
• char
• decimal
• double
• enum
• float
• int
• long
• sbyte
• short
• struct
• uint
• ulong
• ushort

When you pass a value-type variable from one method to another, the system creates a separate copy of a variable in another method. If value got changed in the one method, it wouldn't affect the variable in another method.

                                static void ChangeValue(int x)
                                    {
                                    x =  200;

                                Console.WriteLine(x);
                                    }

                                static void Main(string[] args)
                                    {
                                int i = 100;

                                Console.WriteLine(i);

                                    ChangeValue(i);

                                Console.WriteLine(i);
                                    }
                                

Reference types

Unlike value types, a reference type doesn't store its value directly. Instead, it stores the address where the value is being stored. In other words, a reference type contains a pointer to another memory location that holds the data.

                            static void ChangeReferenceType(Student std2)
                                    {
                                    std2.StudentName = "DotNet";
                                    }

                            static void Main(string[] args)
                                    {
                            Student std1 = new Student();
                                    std1.StudentName = "Palace";

                                    ChangeReferenceType(std1);

                            Console.WriteLine(std1.StudentName);
                                    }
                                

• class
• string
• delegate
• Array

String is a reference type, but it is immutable. It means once we assigned a value, it cannot be changed. If we change a string value, then the compiler creates a new string object in the memory and point a variable to the new memory location. So, passing a string value to a function will create a new variable in the memory, and any change in the value in the function will not be reflected in the original value

The default value of a reference type variable is null when they are not initialized. Null means not refering to any object.

Summary

All the value types derive from System.ValueType, which in-turn, derives from System.Object. Click on next button for next tutorials.

Cheers!