Difference between a.Equals(b) and a == b

In the .NET Framework, data types can be categorized as either value types or reference types based on how they store and access data. A value type directly stores its own data within the variable, while a reference type holds a pointer to the data stored elsewhere in memory.

Value types include primitive types like integers, floating-point numbers, characters, and Booleans, as well as structures and enumerations. These types are stored on the stack and their values are copied when assigned to another variable or passed as method arguments.

On the other hand, reference types include classes, interfaces, delegates, and arrays. They are stored on the heap, and variables of reference types hold a reference (pointer) to the actual data in memory. When a reference type variable is assigned to another variable or passed as an argument, only the reference is copied, not the entire data.

a.Equals(b) or a == b ?

The Object data type is a special type in .NET that can hold references to both value types and reference types. This allows for more flexibility when dealing with different types of data.

To compare values, the Equals() method and the == operator are commonly used. The Equals() method is a method defined by the Object class and can be overridden in derived classes to provide custom comparison logic. The == operator, on the other hand, performs a default equality comparison between two objects and returns a boolean value indicating whether they are equal.

Value Type

For value types, both the == operator and the Equals() method function in a similar manner, comparing two objects based on their values. These mechanisms determine whether the values of two value type objects are equivalent. The == operator performs a default equality comparison between the values, while the Equals() method can be overridden to provide customized comparison logic if needed.

a==b and a.Equals(b) returns true , because in this case both compare two object by value.

Reference Type

In case of Reference Type both works in different way.

sb1 == sb2 returns false and sb1.Equals(sb2) returns true.

== operator compares reference returns true when both references point to the same object and Equals() compares object by value and it will return true if the references refers object which are equivalent.

It's important to note that the behavior of the == operator can vary depending on the type being compared. For value types, the == operator compares the actual values, while for reference types, it compares the references unless the operator is overridden in the class.

Conclusion

Value types store their own data, reference types hold pointers to data, and the Object data type can hold references to both value types and reference types. The Equals() method and the == operator are used for comparison, with the specific behavior determined by the type being compared.