c# SortedList can't inserted items,even not repeated

[mentor]

In the folling codes, Product is a class with SortedList Memeber Components.

Product prod = new Product();   
prod.Components = new sortedList( new IntComparer() );   
prod.Components.Add(0,1);   
prod.Components.Add(1,2);   
 
private class IntComparer : Comparer <int>             
{ 
       public override int Compare(int x, int y) 
       { 
               if   (x   <   y) 
                    return   0; 
               else   if   (x   ==   y) 
                    return   0; 
               else   return   -1; 
        } 
}

The Second Add(1,2) cause an error,

Item has already been added. Key in dictionary: "0" Key being added: "1".

Since 0 and 1 are different key, why this error occur?

In fact these codes had run correctly several days before, may be there are something error elsewhere ?

[mentor]

it's solved. there is something wrong with the comparer

[Plater]

Hehe yeah. Never returned a 1.