参考类型的Equals()的"最佳"规范实现是什么？

Question

为引用类型实现Equals()比看起来更难.我目前的规范实现如下:

public bool Equals( MyClass obj )
{
  // If both refer to the same reference they are equal.
  if( ReferenceEquals( obj, this ) )
    return true;

  // If the other object is null they are not equal because in C# this cannot be null.
  if( ReferenceEquals( obj, null ) )
   return false;

   // Compare data to evaluate equality    
   return _data.Equals( obj._data );
}

public override bool Equals( object obj )
{
  // If both refer to the same reference they are equal.
  if( ReferenceEquals( obj, this ) )
    return true;

  // If the other object is null or is of a different types the objects are not equal. 
  if( ReferenceEquals( obj, null ) || obj.GetType() != GetType() )
    return false;

  // Use type-safe equality comparison
  return Equals( (MyClass)obj );
}

public override int GetHashCode()
{
  // Use data's hash code as our hashcode  
  return _data.GetHashCode();
}

我认为这涵盖了所有角落(继承等),但我可能错了.你们有什么感想？

Answer 1

我不久前为此写了一份相当全面的指南。首先，您的 equals 实现应该是共享的（即，采用对象的重载应该传递给采用强类型对象的重载）。此外，您还需要考虑一些事情，例如您的对象应该是不可变的，因为需要重写 GetHashCode。更多信息请点击这里：

http://gregbeech.com/blog/implementing-object-equality-in-dotnet