IComparer Myth

Hi,

 

Take a look at the below snippet which implements the custom IComparer to compare ‘Movie’ type of Objects.

 

public class Movie {             public string Name;             public string Language;               public Movie()             {             }               public Movie(string name, string language)             {                         This.Name = name;                         This.Language = language;             } }

public class MovieComparer : System.Collections.Generic.IComparer<Movie> {             public string sortExpression;             public string sortOrder;                 public int Compare(Movie x, Movie y)             {                         //return obj1.Name.CompareTo(obj2.Name);  // Simple Way                           try                         {                                     switch (SortOrder)                                     {                                                 case "asc":                                                             if (SortExpression.Equals("Name", StringComparison.OrdinalIgnoreCase))                                                                         return String.Compare(x.Name, y.Name);                                                             else if (SortExpression.Equals("Language", StringComparison.OrdinalIgnoreCase))                                                                         return String.Compare(x.Language, y.Language);                                                             break;                                                   case "dsc":                                                             if (SortExpression.Equals("Name", StringComparison.OrdinalIgnoreCase))                                                                         return String.Compare(y.Name, x.Name);                                                             else if (SortExpression.Equals("Language", StringComparison.OrdinalIgnoreCase))                                                                         return String.Compare(y.Language, x.Language);                                                             break;                                                   default:                                                             break;                                     }                                     return 0;                         }                         catch (ArgumentException ex)                         {                                     throw ex;                         }             } }

 

static void Main()

{

        List<Movie> list = Session["Data"] as List<Movie>;

        List.add(new Movie(‘x’,’y’);

        List.add(new Movie(‘x1’,’y1’);

         --------------

 

        MovieComparer movieComparer = new MovieComparer();

        movieComparer.SortExpression = sortExpression;

        movieComparer.SortOrder = direction;

        list.Sort(movieComparer); 

 

        Session["Data"] = list;

        GridView1.DataSource = Session["Data"] as List<Movie>;

        GridView1.DataBind();

}

 

 

-          By default, the Sort() method uses the IComparable implementation for each element to handle the comparisons necessary for sorting.

-          However, sometimes, though, it is useful to sort the same list in different ways.

-          To accomplish this, an overload of Sort(IComparer comparer) exists that takes an IComparer as a parameter; where IComparer.Compare is then used for the comparisons.

-          This overload allows users of the class to use any of the built-in IComparers or any of their own making (here MovieComparer).

 

 

 

Regards,

Arun Manglick