Best to override Equals() or to overload == operator?

[NeilTrain]

I guess the topic title says it all.

I have a simple class, with two strings and a date time, and would like to prevent duplicates from appearing in a collection, so need to do a quick compare.

Is there a reason Equals() exists when we have the ++ operator? Whats the difference and which is the preferred to use?

 

[AndrewJMarshall]

==" checks for reference equality, but ".Equals(obj)" can be overridden to check for attribute equality.

My guess is that you want to override .Equals.

Andrew

 

[chiph]

Yup. You would override .Equals().

An alternative would be to implement IComparable, which would look like this for comparing against an Id value:

public class Widget : IComparable
{
   override public int CompareTo(object obj)
   {
      // Anything is greater than null
      if( null == obj )
         return 1;

      Widget w = obj as Widget;
      if( null == w )
         throw new ArgumentException("object must be a Widget");

      return this.Id.CompareTo( w.Id );
   }
}

Chip H.

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