rspec/rules/S1210/csharp/rule.adoc

== Why is this an issue?

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

[source,csharp]
----
public class Foo: IComparable  // Noncompliant
{
  public int CompareTo(object obj) { /* ... */ }
}
----

=== Compliant solution

[source,csharp]
----
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);
  }
}
----

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

When implementing {0}, you should also override {1}.


'''
== Comments And Links
(visible only on this page)

include::../comments-and-links.adoc[]

endif::env-github,rspecator-view[]