Equality kinds in c# and equality operator
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.
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);