== Operator (C# Reference)
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.
Remarks
User-defined value types can overload the == operator (see operator). So can user-defined reference types, although by default == behaves as described above for both predefined and user-defined reference types. If == is overloaded, != must also be overloaded. Operations on integral types are generally allowed on enumeration.
Example
// cs_operator_equality.cs
using System;
class MainClass
{
static void Main()
{
// 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);
}
}
Output
True False True False True