Difference between == and Equals() Method in C#


In C#, the equality operator == checks whether two operands are equal or not, and the Object.Equals() method checks whether the two object instances are equal or not.

Internally, == is implemented as the operator overloading method, so the result depends on how that method is overloaded. In the same way, Object.Equals() method is a virtual method and the result depends on the implementation. For example, the == operator and .Equals() compare the values of the two built-in value types variables. if both values are equal then returns true; otherwise returns false.

Example: == Operator
int i = 10, j = 10;

Console.WriteLine(i == j); // true
Console.WriteLine(i.Equals(j)); // true

For the reference type variables, == and .Equals() method by default checks whether two two object instances are equal or not. However, for the string type, == and .Equals() method are implemented to compare values instead of the instances.

Example: == and Equals() with String Type
string str1 = "Hello",
    str2 = "Hello",
    str3 = "hello";

Console.WriteLine(str1 == str2); // true
Console.WriteLine(str1 == str3 ); // false

Console.WriteLine(str1.Equals(str2));// true
Console.WriteLine(str1.Equals(str3));// false

Now, look at the following example:

Example: == and Equals() with Objects
object obj1 = "Hello";
object obj2 = "Hello";

Console.WriteLine(obj1 == obj2); // true
Console.WriteLine(obj1.Equals(obj2)); // true

In the above example, it looks like == and Equals() method compares values. However, they compare instances. C# points two objects to the same memory address if both the values are equal. So, they return true.

Now, check the following:

Example: == and Equals() with Objects
object obj1 = new StringBuilder("Hello");
object obj2 = "Hello";

Console.WriteLine(obj1 == obj2); // false
Console.WriteLine(obj1.Equals(obj2));// false

In the above example, obj1 points to StringBuilder type object and obj2 is string type, so both are different instances even if they have same values. So, == and Equals() method compares the instances and return false because they are different instances.