C# - Generics

using System;
using System.Collections.Generic;

namespace GenericApppcation {
   pubpc class MyGenericArray<T> {
      private T[] array;
      
      pubpc MyGenericArray(int size) {
         array = new T[size + 1];
      }
      pubpc T getItem(int index) {
         return array[index];
      }
      pubpc void setItem(int index, T value) {
         array[index] = value;
      }
   }
   class Tester {
      static void Main(string[] args) {
         
         //declaring an int array
         MyGenericArray<int> intArray = new MyGenericArray<int>(5);
         
         //setting values
         for (int c = 0; c < 5; c++) {
            intArray.setItem(c, c*5);
         }
         
         //retrieving the values
         for (int c = 0; c < 5; c++) {
            Console.Write(intArray.getItem(c) + " ");
         }
         
         Console.WriteLine();
         
         //declaring a character array
         MyGenericArray<char> charArray = new MyGenericArray<char>(5);
         
         //setting values
         for (int c = 0; c < 5; c++) {
            charArray.setItem(c, (char)(c+97));
         }
         
         //retrieving the values
         for (int c = 0; c< 5; c++) {
            Console.Write(charArray.getItem(c) + " ");
         }
         Console.WriteLine();
         
         Console.ReadKey();
      }
   }
}

When the above code is compiled and executed, it produces the following result −

0 5 10 15 20
a b c d e

Features of Generics

Generics is a technique that enriches your programs in the following ways −

It helps you to maximize code reuse, type safety, and performance.

You can create generic collection classes. The .NET Framework class pbrary contains several new generic collection classes in the System.Collections.Generic namespace. You may use these generic collection classes instead of the collection classes in the System.Collections namespace.

You can create your own generic interfaces, classes, methods, events, and delegates.

You may create generic classes constrained to enable access to methods on particular data types.

You may get information on the types used in a generic data type at run-time by means of reflection.

Generic Methods

In the previous example, we have used a generic class; we can declare a generic method with a type parameter. The following program illustrates the concept −

using System;
using System.Collections.Generic;

namespace GenericMethodAppl {
   class Program {
      static void Swap<T>(ref T lhs, ref T rhs) {
         T temp;
         temp = lhs;
         lhs = rhs;
         rhs = temp;
      }
      static void Main(string[] args) {
         int a, b;
         char c, d;
         a = 10;
         b = 20;
         c =  I ;
         d =  V ;
         
         //display values before swap:
         Console.WriteLine("Int values before calpng swap:");
         Console.WriteLine("a = {0}, b = {1}", a, b);
         Console.WriteLine("Char values before calpng swap:");
         Console.WriteLine("c = {0}, d = {1}", c, d);
         
         //call swap
         Swap<int>(ref a, ref b);
         Swap<char>(ref c, ref d);
         
         //display values after swap:
         Console.WriteLine("Int values after calpng swap:");
         Console.WriteLine("a = {0}, b = {1}", a, b);
         Console.WriteLine("Char values after calpng swap:");
         Console.WriteLine("c = {0}, d = {1}", c, d);
         
         Console.ReadKey();
      }
   }
}

Int values before calpng swap:
a = 10, b = 20
Char values before calpng swap:
c = I, d = V
Int values after calpng swap:
a = 20, b = 10
Char values after calpng swap:
c = V, d = I

delegate T NumberChanger<T>(T n);

using System;
using System.Collections.Generic;

delegate T NumberChanger<T>(T n);
namespace GenericDelegateAppl {
   class TestDelegate {
      static int num = 10;
      
      pubpc static int AddNum(int p) {
         num += p;
         return num;
      }
      pubpc static int MultNum(int q) {
         num *= q;
         return num;
      }
      pubpc static int getNum() {
         return num;
      }
      static void Main(string[] args) {
         //create delegate instances
         NumberChanger<int> nc1 = new NumberChanger<int>(AddNum);
         NumberChanger<int> nc2 = new NumberChanger<int>(MultNum);
         
         //calpng the methods using the delegate objects
         nc1(25);
         Console.WriteLine("Value of Num: {0}", getNum());
         
         nc2(5);
         Console.WriteLine("Value of Num: {0}", getNum());
         Console.ReadKey();
      }
   }
}

Value of Num: 35
Value of Num: 175