Làm th? nào ð? s? d?ng giao di?n IComparable và IComparer trong Visual C#

IComparable

// Implement IComparable CompareTo method - provide default sort order.
int IComparable.CompareTo(object obj)
{
   car c=(car)obj;
   return String.Compare(this.make,c.make);

}
				

IComparer

private class sortYearAscendingHelper : IComparer
{
   int IComparer.Compare(object a, object b)
   {
      car c1=(car)a;
      car c2=(car)b;
      if (c1.year > c2.year)
         return 1;
      if (c1.year < c2.year)
         return -1;
      else
         return 0;
   }
}
				

public static IComparer sortYearAscending()
{      
   return (IComparer) new sortYearAscendingHelper();
}
				

Ví d?-by-step

1. Trong Visual C#, t?o ra m?t d? án ?ng d?ng giao di?n ði?u khi?n m?i. Tên ?ng d?ng ConsoleEnum.
2. Ð?i tên Program.cs nhý Host.cs, và sau ðó thay th? m? v?i ðo?n m? sau.
   
   Chuì yì Trong ph?ng thu tr?c quan.NET 2003, ð?i tên Class1.cs nhý Host.cs.

   using System;
   
   namespace ConsoleEnum
   {
      class host
      {
         [STAThread]
         static void Main(string[] args)
         {
            // Create an arary of car objects.      
            car[] arrayOfCars= new car[6]
            {
               new car("Ford",1992),
               new car("Fiat",1988),
               new car("Buick",1932),
               new car("Ford",1932),
               new car("Dodge",1999),
               new car("Honda",1977)
            };
         
            // Write out a header for the output.
            Console.WriteLine("Array - Unsorted\n");
   
            foreach(car c in arrayOfCars)
               Console.WriteLine(c.Make + "\t\t" + c.Year);
         
            // Demo IComparable by sorting array with "default" sort order.
            Array.Sort(arrayOfCars);
            Console.WriteLine("\nArray - Sorted by Make (Ascending - IComparable)\n");
   
            foreach(car c in arrayOfCars)
               Console.WriteLine(c.Make + "\t\t" + c.Year);
   
            // Demo ascending sort of numeric value with IComparer.
            Array.Sort(arrayOfCars,car.sortYearAscending());
            Console.WriteLine("\nArray - Sorted by Year (Ascending - IComparer)\n");
   
            foreach(car c in arrayOfCars)
               Console.WriteLine(c.Make + "\t\t" + c.Year);
   
            // Demo descending sort of string value with IComparer.
            Array.Sort(arrayOfCars,car.sortMakeDescending());
            Console.WriteLine("\nArray - Sorted by Make (Descending - IComparer)\n");
   
            foreach(car c in arrayOfCars)
               Console.WriteLine(c.Make + "\t\t" + c.Year);
   
            // Demo descending sort of numeric value using IComparer.
            Array.Sort(arrayOfCars,car.sortYearDescending());
            Console.WriteLine("\nArray - Sorted by Year (Descending - IComparer)\n");
   
            foreach(car c in arrayOfCars)
               Console.WriteLine(c.Make + "\t\t" + c.Year);
        
            Console.ReadLine();
         }
      }
   }
   					

3. Thêm m?t l?p h?c cho d? án. Tên l?p xe.
4. Thay th? m? trong Car.cs v?i nh?ng ði?u sau ðây:

   using System;
   using System.Collections;
   namespace ConsoleEnum
   {   
      public class car : IComparable
      {      
         // Beginning of nested classes.
   
         // Nested class to do ascending sort on year property.
         private class sortYearAscendingHelper: IComparer
         {
            int IComparer.Compare(object a, object b)
            {
               car c1=(car)a;
               car c2=(car)b;
   
               if (c1.year > c2.year)
                  return 1;
   
               if (c1.year < c2.year)
                  return -1;
   
               else
                  return 0;
            }
         }
   
         // Nested class to do descending sort on year property.
         private class sortYearDescendingHelper: IComparer
         {
            int IComparer.Compare(object a, object b)
            {
               car c1=(car)a;
               car c2=(car)b;
   
               if (c1.year < c2.year)
                  return 1;
   
               if (c1.year > c2.year)
                  return -1;
   
               else
                  return 0;
            }
         }
   
         // Nested class to do descending sort on make property.
         private class sortMakeDescendingHelper: IComparer
         {
            int IComparer.Compare(object a, object b)
            {
               car c1=(car)a;
               car c2=(car)b;
                return String.Compare(c2.make,c1.make);
            }
         }
   
         // End of nested classes.
   
         private int year;
         private string make;
           
         public car(string Make,int Year)
         {
            make=Make;
            year=Year;
         }
   
         public int Year
         {
            get  {return year;}
            set {year=value;}
         }
   
         public string Make
         {
            get {return make;}
            set {make=value;}
         }
   
         // Implement IComparable CompareTo to provide default sort order.
         int IComparable.CompareTo(object obj)
         {
            car c=(car)obj;
            return String.Compare(this.make,c.make);
         }
   
         // Method to return IComparer object for sort helper.
         public static IComparer sortYearAscending()
         {      
            return (IComparer) new sortYearAscendingHelper();
         }
   
         // Method to return IComparer object for sort helper.
         public static IComparer sortYearDescending()
         {      
            return (IComparer) new sortYearDescendingHelper();
         }
   
         // Method to return IComparer object for sort helper.
         public static IComparer sortMakeDescending()
         {      
           return (IComparer) new sortMakeDescendingHelper();
         }
   
      }
   }
   					

5. Ch?y các d? án. Ð?u ra sau ðây s? xu?t hi?n trong c?a s? giao di?n ði?u khi?n:

   Array - Unsorted
   
   Ford            1992
   Fiat            1988
   Buick           1932
   Ford            1932
   Dodge           1999
   Honda           1977
   
   Array - Sorted by Make (Ascending - IComparable)
   
   Buick           1932
   Dodge           1999
   Fiat            1988
   Ford            1932
   Ford            1992
   Honda           1977
   
   Array - Sorted by Year (Ascending - IComparer)
   
   Ford            1932
   Buick           1932
   Honda           1977
   Fiat            1988
   Ford            1992
   Dodge           1999
   
   Array - Sorted by Make (Descending - IComparer)
   
   Honda           1977
   Ford            1932
   Ford            1992
   Fiat            1988
   Dodge           1999
   Buick           1932
   
   Array - Sorted by Year (Descending - IComparer)
   
   Dodge           1999
   Ford            1992
   Fiat            1988
   Honda           1977
   Buick           1932
   Ford            1932
   					

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