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Operator overloads have named alternates

TypeName

OperatorOverloadsHaveNamedAlternates

CheckId

CA2225

Category

Microsoft.Usage

Breaking Change

NonBreaking

An operator overload was detected, and the expected named alternative method was not found.

Operator overloading permits the use of symbols to represent computations for a type. For example, a type that overloads the plus symbol (+) for addition would typically have an alternative member named 'Add'. The named alternative member provides access to the same functionality as the operator, and is provided for developers programming in languages that do not support overloaded operators, such as Visual Basic .NET.

This rule examines the operators listed in the following table.

C# symbol Alternate name

+, +=

Add

-, -=

Subtract

*, *=

Multiply

/, /=

Divide

%, %=

Mod

>, >=, <, <=, !=

Compare

==

Equals

The rule also checks implicit and explicit cast operators in a type (SomeType) by checking for methods named ToSomeType and FromSomeType.

In C#, when a binary operator is overloaded, the corresponding assignment operator, if any, is also implicitly overloaded.

To fix a violation of this rule, implement the alternative method for the operator; name it using the recommended alternative name.

Do not exclude a warning from this rule if you are implementing a shared library. Applications can ignore a warning from this rule.

The following example defines a structure that violates this rule.

using System;

namespace UsageLibrary
{
    public struct Point
    {
        private int x,y;
        
        public Point(int x, int y)
        {
            this.x = x;
            this.y = y;
        }

        public override string ToString()
        {
            return String.Format("({0},{1})",x,y);
        }

        // Violates rule: OperatorOverloadsHaveNamedAlternates.
        public static Point operator+(Point a, Point b)
        { 
            return new Point(a.x + b.x, a.y + b.y);
        }

        public int X {get {return x;}}
        public int Y {get {return x;}}
    }
}

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