Equality kinds in c# and equality operator C# with Example

In C#, there are two different kinds of equality: reference equality and value equality. Value equality is the 
commonly understood meaning of equality: it means that two objects contain the same values. For example, two 
integers with the value of 2 have value equality. Reference equality means that there are not two objects to 
compare. Instead, there are two object references, both of which refer to the same object. 
object a = new object(); 
object b = a; 
System.Object.ReferenceEquals(a, b); //returns true 
For predefined value types, the equality operator (==) returns true if the values of its operands are equal, false 
otherwise. For reference types other than string, == returns true if its two operands refer to the same object. For 
the string type, == compares the values of the strings. 
// Numeric equality: True 
Console.WriteLine((2 + 2) == 4); 
// Reference equality: different objects, 
// same boxed value: False. 
object s = 1; 
object t = 1; 
Console.WriteLine(s == t); 
// Define some strings: 
string a = "hello"; 
string b = String.Copy(a); 
string c = "hello"; 
// Compare string values of a constant and an instance: True 
Console.WriteLine(a == b); 
// Compare string references; 
// a is a constant but b is an instance: False. 
Console.WriteLine((object)a == (object)b); 
// Compare string references, both constants 
// have the same value, so string interning 
// points to  same reference: True. 
Console.WriteLine((object)a == (object)c);