Generic allows you to delay writing specifications for the data types of programming elements in a class or method until it is actually used in the program. In other words, generics allow you to write a class or method that works with any data type.
You can write the specification of a class or method through alternative parameters of the data type. When the compiler encounters a function call tothe constructor or method of a class, it generates code to handle the specified data type. The following simple example will help you understand this concept: When the above code is compiled and executed, it produces the following results: Using generics is a technique to enhance the functionality of a program, which is shown in the following aspects: It helps you maximize code reuse, protect types, and improve performance. You can create generic collection classes. The You can create your own generic interfaces, generic classes, generic methods, generic events, and generic delegates. You can constrain generic classes to access methods of specific data types. Information about the types used in generic data types can be obtained at run time by using reflection. In the above example, we have used generic classes, and we can declare generic methods through type parameters. The following procedure illustratesthis concept: When the above code is compiled and executed, it produces the following results: You can define a generic delegate through type parameters. For example: The following example demonstrates the use of delegates: When the above code is compiled and executed, it produces the following results: 1.60.1. Example #
using System; using System.Collections.Generic; namespace GenericApplication { public class MyGenericArray<T> { private T[] array; public MyGenericArray(int size) { array = new T[size + 1]; } public T getItem(int index) { return array[index]; } public void setItem(int index, T value) { array[index] = value; } } class Tester { static void Main(string[] args) { // Declare an integer array MyGenericArray<int> intArray = new MyGenericArray<int>(5); // Setting values for (int c = 0; c < 5; c++) { intArray.setItem(c, c*5); } // Get Value for (int c = 0; c < 5; c++) { Console.Write(intArray.getItem(c) + " "); } Console.WriteLine(); // Declare 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)); } // Get Value for (int c = 0; c < 5; c++) { Console.Write(charArray.getItem(c) + " "); } Console.WriteLine(); Console.ReadKey(); } } }
0 5 10 15 20 a b c d e
Characteristics of Generic #
.NET framework class library is available in the System.Collections.Generic . The namespace contains some new generic collection classes. You can use these generic collection classes instead of System.Collections .Generic method #
1.60.2. Example #
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 swapping Console.WriteLine("Int values before calling swap:"); Console.WriteLine("a = {0}, b = {1}", a, b); Console.WriteLine("Char values before calling 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 swapping Console.WriteLine("Int values after calling swap:"); Console.WriteLine("a = {0}, b = {1}", a, b); Console.WriteLine("Char values after calling swap:"); Console.WriteLine("c = {0}, d = {1}", c, d); Console.ReadKey(); } } }
Int values before calling swap: a = 10, b = 20 Char values before calling swap: c = I, d = V Int values after calling swap: a = 20, b = 10 Char values after calling swap: c = V, d = I
Generic delegation #
delegate T NumberChanger<T>(T n);
1.60.3. Example #
using System; using System.Collections.Generic; delegate T NumberChanger<T>(T n); namespace GenericDelegateAppl { class TestDelegate { static int num = 10; public static int AddNum(int p) { num += p; return num; } public static int MultNum(int q) { num *= q; return num; } public static int getNum() { return num; } static void Main(string[] args) { // Create Delegate Instance NumberChanger<int> nc1 = new NumberChanger<int>(AddNum); NumberChanger<int> nc2 = new NumberChanger<int>(MultNum); // Calling methods using 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