#420 – Laundry List for Implementing Value Equality and IComparable

To implement value equality (equivalence) in a reference type, you should do the following:

• Override Object.Equals
  • In Object.Equals, call the type-specific Equals method using the as operator
• Implement IEquatable<T> by adding a type-specific Equals method
  • Check for null using ReferenceEquals method
  • Call base class’ Equals method to compare fields that exist in the base class if it also checks for value equality
  • Check for equivalence by comparing individual fields
• Override GetHashCode, generating a hash code based on fields used for equivalence
• Overload == operator
  • Check for 1st parameter being null, compare to 2nd parameter
  • Call 1st parameter’s type-specific Equals method
• Overload != operator, invoking the == operator
• Implement IComparable<T>, adding a CompareTo method
  • Check for equivalence using Equals method, then compare individual fields
• Overload < and > operators
  • Check for 1st parameter being null
  • Call 1st parameter’s CompareTo method
• Overload <= and >= operators
  • Calculate a result using the <, > and == operators