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Code Analyzer for C#

There is a newer version: 10.2.0.105762

Why is this an issue?
Making a base call when overriding a method is generally a good idea, but not in the case of GetHashCode and Equals for classes that directly extend Object.
These methods are based on the object’s reference, meaning that no two objects that use those base methods can be equal or have the same
hash.
Exceptions
This rule doesn’t report on guard conditions checking for reference equality. For example:
public override bool Equals(object obj)
{
  if (base.Equals(obj)) // Compliant, it's a guard condition.
  {
    return true;
  }
  ...
}

How to fix it
Code examples
Noncompliant code example
var m1 = new MyClass(2);
var m2 = new MyClass(2);

m1.Equals(m2) // False
m1.GetHashCode(); // 43942919
m2.GetHashCode(); // 59941935

class MyClass
{
    private readonly int x;
    public MyClass(int x) =>
        this.x = x;

    public override bool Equals(Object obj) =>
        base.Equals();

    public override int GetHashCode() =>
        x.GetHashCode() ^ base.GetHashCode(); // Noncompliant, base.GetHashCode returns a code based on the objects reference
}

Compliant solution
var m1 = new MyClass(2);
var m2 = new MyClass(2);

m1.Equals(m2) // True
m1.GetHashCode(); // 2
m2.GetHashCode(); // 2

class MyClass
{
    private readonly int x;
    public MyClass(int x) =>
        this.x = x;

    public override bool Equals(Object obj) =>
        this.x == ((MyClass)obj).x;

    public override int GetHashCode() =>
        x.GetHashCode()
}

Resources
Documentation

   Microsoft Learn - Object.GetHashCode Method
  
   Microsoft Learn - Object.Equals Method