The Comparer class is used to compare two objects of the same type. The Compare( ) method takes two objects. If the first object is less than the second, a negative value is returned. If the first object is greater than the second, a positive value is returned. If the objects are equal, zero is returned. The comparisons of strings are case-sensitive. For case-insensitive string comparisons, use CaseInsensitiveComparer. You can obtain a standard comparer that uses the System.Globalization.InvariantCulture rules for string comparisons by using the CaseInsensitiveComparer instance returned from the static DefaultInvariant property.

public sealed class Comparer : IComparer {
// Public Constructors
   public Comparer(System.Globalization.CultureInfo culture);
// Public Static Fields
   public static readonly Comparer Default;           
// =System.Collections.Comparer
   public static readonly Comparer DefaultInvariant;  
// =System.Collections.Comparer
// Public Instance Methods
   public int Compare(object a, object b);           
// implements IComparer
}