Use of Distinct with list of Custom Object

Question

How can I make the Distinct() method work with a list of custom object(Href in this case), here is what the current object looks like:

    public class Href : IComparable, IComparer<Href>
    {
            public Uri URL { get; set; }
            public UrlType URLType { get; set; } 

           public Href(Uri url, UrlType urltype)
           {
                   URL = url;
                   URLType = urltype;
           }


           #region IComparable Members

           public int CompareTo( object obj )
           {
                   if(obj is Href)
                   {
                           return URL.ToString().CompareTo( ( obj as Href ).URL.ToString() );
                   } 
                   else
                           throw new ArgumentException("Wrong data type.");
           }

           #endregion

           #region IComparer<Href> Members

           int IComparer<Href>.Compare( Href x , Href y )
           {
                   return string.Compare( x.URL.ToString() , y.URL.ToString() );
           }

           #endregion
    }

Answer 1

You need to override Equals and GetHashCode.

GetHashCode should return the same value for all instances that are considered equal.

For example:

public override bool Equals(object obj) { 
    Href other = obj as Href;
    return other != null && URL.Equals(other.URL);
} 

public override int GetHashCode() { 
    return URL.GetHashCode();
} 

Since .Net's Uri class overrides GetHashCode, you can simply return the URL's hashcode.

Answer 2

You could grab a copy of aku's comparer (beware of the GetHashCode implementation however), and then write something like this

hrefList.Distinct(new Comparer<Href>((h1,h2)=>h1.URL==h2.URL))