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Code Analyzer for C#

There is a newer version: 10.2.0.105762

Why is this an issue?
Suppose you override Object.Equals in a type, you must also
override Object.GetHashCode. If two objects are equal according
to the Equals method, then calling GetHashCode on each of them must yield the same integer. If this is not the case, many
collections, such as a Hashtable or a Dictionary won’t handle class instances correctly.
In order to not have unpredictable behavior, Equals and GetHashCode should be either both inherited, or both
overridden.
How to fix it
When you override Equals then you have to also override GetHashCode. You have to override both of them, or simply inherit
them.
Code examples
Noncompliant code example
class MyClass   // Noncompliant: should also override GetHashCode
{
    public override bool Equals(object obj)
    {
        // ...
    }
}

Compliant solution
class MyClass
{
    public override bool Equals(object obj)
    {
        // ...
    }

    public override int GetHashCode()
    {
        // ...
    }
}

Resources
Documentation

   CWE - CWE-581 - Object Model Violation: Just One of Equals and Hashcode Defined 
   Object.Equals Method 
   Object.GetHashCode Method 
   Hashtable class 
   Dictionary<TKey,TValue> Class