rspec/rules/S1210/csharp/rule.adoc

When you implement ``IComparable`` or ``IComparable<T>`` on a class you should also override ``Equals(object)`` and overload the comparison operators (``==``, ``!=``, ``<``, ``<=``, ``>``, ``>=``). That's because the CLR cannot automatically call your ``CompareTo`` implementation from ``Equals(object)`` or from the base comparison operator implementations. Additionally, it is best practice to override ``GetHashCode`` along with ``Equals``.

This rule raises an issue when a class implements ``IComparable`` without also overriding ``Equals(object)`` and the comparison operators.

== Noncompliant Code Example

----
public class Foo: IComparable  // Noncompliant
{
  public int CompareTo(object obj) { /* ... */ }
}
----

== Compliant Solution

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public class Foo: IComparable
{
  public int CompareTo(object obj) { /* ... */ }
  public override bool Equals(object obj)
  {
    var other = obj as Foo;
    if (object.ReferenceEquals(other, null))
    {
      return false;
    }
    return this.CompareTo(other) == 0;
  }
  public int GetHashCode() { /* ... */ }
  public static bool operator == (Foo left, Foo right) 
  {
    if (object.ReferenceEquals(left, null))
    {
      return object.ReferenceEquals(right, null);
    }
    return left.Equals(right);
  }
  public static bool operator > (Foo left, Foo right) 
  {
    return Compare(left, right) > 0;
  }
  public static bool operator < (Foo left, Foo right) 
  {
    return Compare(left, right) < 0;
  }
  public static bool operator != (Foo left, Foo right) 
  {
    return !(left == right);
  }
}
----