Equality Implementation in C#

The equality pattern I like to see in C# is as follows:

For entity type classes

“Many objects are not fundamentally defined by their attributes, but rather by a thread of continuity and identity.” -Eric Evans

/// <summary>
/// Entity object where identity is based on identifier (e.g. Person)
/// </summary>
class Entity : IEquatable<Entity>
{
private readonly Int32 _Identifier;
public Entity(Int32 identifier)
{
_Identifier = identifier;
}
public override bool Equals(object obj)
{
var result = Equals(obj as Entity);
return result;
}
public override int GetHashCode()
{
var result = _Identifier.GetHashCode();
return result;
}
public bool Equals(Entity other)
{
if (ReferenceEquals(other, null))
return false;
var result = _Identifier == other._Identifier;
return result;
}
// optional operators
public static Boolean operator ==(Entity target, Entity other)
{
if (ReferenceEquals(target, other))
return true;
if (ReferenceEquals(target, null))
return false;
var result = target.Equals(other);
return result;
}
public static Boolean operator !=(Entity target, Entity other)
{
var result = !(target == other);
return result;
}
}

For value type classes

“Many objects have no conceptual identity. These objects describe characteristics of a thing.” -Eric Evans

/// <summary>
/// Value object where identity is based on state (e.g. Money)
/// </summary>
class Value :IEquatable<Value>
{
private readonly Int32 _Property1, _Property2;
public Value(Int32 property1, Int32 property2)
{
_Property1 = property1;
_Property2 = property2;
}
public override bool Equals(object obj)
{
var result = Equals(obj as Value);
return result;
}
public bool Equals(Value other)
{
if (ReferenceEquals(other, null))
return false;
var result =
_Property1 == other._Property1 &&
_Property2 == other._Property2;
return result;
}
public override int GetHashCode()
{
var result =
_Property1.GetHashCode() ^
_Property2.GetHashCode();
return result;
}
// optional operators
public static Boolean operator == (Value target, Value other)
{
if (ReferenceEquals(target, other))
return true;
if (ReferenceEquals(target, null))
return false;
var result = target.Equals(other);
return result;
}
public static Boolean operator !=(Value target, Value other)
{
var result = !(target == other);
return result;
}
}

Equality Implementation in C#

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