ca1046.md

title	ms.date	ms.topic	f1_keywords	helpviewer_keywords	ms.assetid	author	ms.author	manager	ms.workload
CA1046: Do not overload operator equals on reference types	11/04/2016	reference	DoNotOverloadOperatorEqualsOnReferenceTypes CA1046	CA1046 DoNotOverloadOperatorEqualsOnReferenceTypes	c1dfbfe3-63f9-4005-a81a-890427b77e79	mikejo5000	mikejo	jillfra	multiple

CA1046: Do not overload operator equals on reference types

Item	Value
CheckId	CA1046
Category	Microsoft.Design
Breaking change	Breaking

Cause

A public or nested public reference type overloads the equality operator.

Rule description

For reference types, the default implementation of the equality operator is almost always correct. By default, two references are equal only if they point to the same object.

How to fix violations

To fix a violation of this rule, remove the implementation of the equality operator.

When to suppress warnings

It is safe to suppress a warning from this rule when the reference type behaves like a built-in value type. If it is meaningful to do addition or subtraction on instances of the type, it is probably correct to implement the equality operator and suppress the violation.

Example

The following example demonstrates the default behavior when comparing two references.

[!code-csharpFxCop.Design.RefTypesNoEqualityOp#1]

Example

The following application compares some references.

[!code-csharpFxCop.Design.TestRefTypesNoEqualityOp#1]

This example produces the following output:

a = new (2,2) and b = new (2,2) are equal? No
c and a are equal? Yes
b and a are == ? No
c and a are == ? Yes

Configurability

If you're running this rule from FxCop analyzers (and not with legacy analysis), you can configure which parts of your codebase to run this rule on, based on their accessibility. For example, to specify that the rule should run only against the non-public API surface, add the following key-value pair to an .editorconfig file in your project:

dotnet_code_quality.ca1046.api_surface = private, internal

You can configure this option for just this rule, for all rules, or for all rules in this category (Design). For more information, see Configure FxCop analyzers.

Related rules

CA1013: Overload operator equals on overloading add and subtract

See also

• xref:System.Object.Equals%2A?displayProperty=fullName
• Equality Operators