Generic Methods

Generics in C#

Generic in C# means common to or applicable to an entire class. As most of the developers think Generic is to define type-safe data structures without committing to actual data types, but is it the only reason why Generics are for?The answer is BIG NO.

In this article we will focus on what other important aspect can be achieved in our daily programming by using Generic. We will see how to use Generic and avoid method overloading.

The below program shows the use of method overloading to display content of int, double & char array.

using System;
class OverloadedMethods
{
static void Main(string[] args)
{
  // create arrays of int, double and char
  int[] intArray = { 1, 2, 3, 4, 5, 6 };
  double[] doubleArray = { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7 };
  char[] charArray = { 'H', 'E', 'L', 'L', 'O' };

  Console.WriteLine("Array intArray contains:");
  DisplayArray(intArray); // pass an int array argument
  Console.WriteLine("Array doubleArray contains:");
  DisplayArray(doubleArray); // pass a double array argument
  Console.WriteLine("Array charArray contains:");
  DisplayArray(charArray); // pass a char array argument
} // end Main
// output int array
static void DisplayArray(int[] inputArray)
{
  foreach (int element in inputArray)
      Console.Write(element + " ");
  Console.WriteLine("\n");
} // end method DisplayArray
// output double array
static void DisplayArray(double[] inputArray)
{
  foreach (double element in inputArray)
      Console.Write(element + " ");
  Console.WriteLine("\n");
} // end method DisplayArray
// output char array
static void DisplayArray(char[] inputArray)
{
  foreach (char element in inputArray)
      Console.Write(element + " ");
  Console.WriteLine("\n");
} // end method DisplayArray
} // end class OverloadedMethods

When we run the program output would be following:

For Array intArray contains:
1 2 3 4 5 6

For Array doubleArray contains:21.1, 22.2, 23.3, 24.4, 25.5

For Array charArray contains:
H E L L O

This looks pretty simple, but did you notice we had to write the same logic thrice for int, double and char. What if we had do write similar processing for all the data types, it would have taken hundred's of line.

To overcome this from C# 2.0 Generic methods have been introduced. If we have similar operation to be performed by several overloaded methods we can write a single generic method declaration that can be called at different times with arguments of different types. Based on the types of the arguments passed to the generic method, the compiler handles each method call appropriately. All generic method declarations have a type parameter list delimited by angle brackets (<> in this example) that follows the method's name.

Below we see the same code written using Generic method.

using System;
using System.Collections.Generic;

class MethodGeneric
{
    static void Main(string[] args)
    {
        // create arrays of int, double and char
        int[] intArray = { 1, 2, 3, 4, 5, 6 };
        double[] doubleArray = { 21.1, 22.2, 23.3,24.4, 25.5};
        char[] charArray = { 'H', 'E', 'L', 'L', 'O'};

        Console.WriteLine("Array intArray contains:");
        PrintArray(intArray); // pass an int array argument
        Console.WriteLine("Array doubleArray contains:");
        PrintArray(doubleArray); // pass a double array argument
        Console.WriteLine("Array charArray contains:");
        PrintArray(charArray); // pass a char array argument
    } // end Main

    // output array of all types
    static void PrintArray<T>(ref T inputArray)
    {
        foreach (var element in inputArray)
            Console.Write(element + " ");
        Console.WriteLine("\n");
    } // end method PrintArray

} // end class MethodGeneric

This program has the same output as the previous one, but we reduced the number of lines in the program. A generic method’s body is declared like that of any other method. Just like type declarations, method declarations can be generic i.e., parameterized by one or more type parameters. A type parameter is an identifier that is used in place of actual type names. The type parameters can be used to declare the return type, the parameter types and the local variable types in a generic method declaration. The type parameters act as placeholders for the types of the arguments passed to the generic method.