[Solved] Difference between == and Equals in C# [duplicate]

Question

== is an operator, which, when not overloaded means “reference equality” for classes (and field-wise equality for structs), but which can be overloaded. A consequence of it being an overload rather than an override is that it is not polymorphic.

Equals is a virtual method; this makes it polymorphic, but means you need to be careful not to call it on null instances.

As a rule of thumb:

if you know the type of something, and know it has an == overload (most core types such as string, int, float, etc have == meanings), then use ==
if you don’t know the type, Equals(a,b) may be recommended, as this avoids the null issue
if you really want to check for the same instance (reference equality), consider using ReferenceEquals(a,b), as this will work even if the == is overloaded and Equals overridden
when using generics, consider EqualityComparer<T>.Default.Equals(a,b) which avoids the null issue, supports Nullable-of-T, and supports IEquatable-of-T

Accepted Answer

== is an operator, which, when not overloaded means “reference equality” for classes (and field-wise equality for structs), but which can be overloaded. A consequence of it being an overload rather than an override is that it is not polymorphic.

Equals is a virtual method; this makes it polymorphic, but means you need to be careful not to call it on null instances.

As a rule of thumb:

if you know the type of something, and know it has an == overload (most core types such as string, int, float, etc have == meanings), then use ==
if you don’t know the type, Equals(a,b) may be recommended, as this avoids the null issue
if you really want to check for the same instance (reference equality), consider using ReferenceEquals(a,b), as this will work even if the == is overloaded and Equals overridden
when using generics, consider EqualityComparer<T>.Default.Equals(a,b) which avoids the null issue, supports Nullable-of-T, and supports IEquatable-of-T