Generics in C#

Generics Explained in C#

Generic is a type that is used to define a class, structure, interface or method with placeholders (type parameters) to indicate that they can store or use one or more of the types. In c#, the compiler will replace placeholders with the specified type at compile time.

 Mostly we use generics with collections and the methods that operate on them to specify a type of objects to be stored in a collection. The generics are introduced in .NET Framework 2.0 with a new namespace called System.Collections.Generic. 

 Generics are useful to improve the code reusability, type safety, and the performance when compared with the non-generic types such as arraylist.

 Generics Declaration in C#

To define a class or method as generic, then we need to use a type parameter as a placeholder with an angle (<>) brackets.

 The following is an example of defining a generic class with type parameter (T) as a placeholder with an angle (<>) brackets.

     public class GenericClassExample<T>

    {

        public T message;

        public void GenericMethod(T name, T location)

        {

            Console.WriteLine($"{message}");

            Console.WriteLine($"Name: {name}");

            Console.WriteLine($"Location: {location}");

        }

    }

From the above class, we created a class (GenericClassExample) with one parameter (message) and method (GenericMethod) using type parameter (T) as placeholder with an angle (<>) brackets.

 

Here, the angle (<>) brackets will indicate a GenericClassExample is generic and type parameter (T) is used to accept a requested type. The type parameter name can be anything like X or U or etc. based on our needs.

 

Generally, while creating an instance of the class we need to specify an actual type, then the compiler will replace all the type parameters such as T or U or X, etc. with specified actual type.

Generic Class Example in C#

The following is an example of creating a generic class using type parameter (T) with angle (<>) brackets in C#.

 

using System;

namespace CsharpnaijaTutorial

{

    public class GenericClassExample<T>

    {

        public T message;

        public void GenericMethod(T name, T location)

        {

            Console.WriteLine("{0}", message);

            Console.WriteLine("Name: {0}", name);

            Console.WriteLine("Location: {0}", location);

        }

    }

 

    class Program

    {

        static void Main(string[] args)

        {

            Console.WriteLine("****Generics Example****");

            // Instantiate Generic Class, string is the type argument

            GenericClassExample<string> genericclass = new GenericClassExample<string>

            {

                message = "Welcome to Csharpnaija"

            };

            genericclass.GenericMethod("Musa Gadabs", "Abuja");

            Console.ReadLine();

        }

    }

}

 

C# Generic Class as Base / Derived Class

In C#, you can use the generic class as a base class, but we need to provide a type instead of type parameter for the base class because there is no way to send a required type argument to instantiate a base class at run time.

 

Following is the example of using a generic class as a base class in C# programming language.

// Correct way of using Generic class without Error

class DClass1 : GenericClassExample<string>

{

    // implementation

}

 

// Compile Time Error

//class DClass2 : GenericClassExample<T> {

// implementation

//}

 

C# Generic Methods

In C#, if we define a method with type parameter, then it is called a generic method. The example code shows how to define a generic method with type parameter using angle (<>) brackets.

 

public void GenericMethod<T>(T a, T b)

{

    // Implementation

}

 

This generic method can be called either by specifying the type of argument or without an argument as shown below.

 

GenericMethod<int>(1, 2);

//or

GenericMethod(1, 2);

 

C# Generic Method Example

In C#, you can call a generic method by passing any type of arguments. The following is an example of defining a generic method in C# programming language.

 

using System;

namespace CsharpnaijaTutorial

{

    public class SampleClass

    {

        public void GenericMethod<T>(T a, T b)

        {

            Console.WriteLine("Param1: {0}", a);

            Console.WriteLine("Param2: {0}", b);

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            Console.WriteLine("****Generics Method Example****");

            SampleClass sample = new SampleClass();

            sample.GenericMethod<int>(1, 2);

            sample.GenericMethod("Musa Gadabs", "Abuja");

            Console.ReadLine();

        }

    }

}

 

C# Generic Delegates

A generic delegate will be same as a normal delegate but the only difference is a generic delegate   will have a generic type with angle (<>) brackets.

 

The following is an example of defining a generic delegate in C#.

 

using System;

namespace CsharpnaijaTutorial

{

    // Declare Generic Delegate

    public delegate T SampleDelegate<T>(T a, T b);

    class MathOperations

    {

        public int Add(int a, int b)

        {

            return a + b;

        }

        public int Subtract(int x, int y)

        {

            return x - y;

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            Console.WriteLine("****Generic Delegate Example****");

            MathOperations mathOps = new MathOperations();

            // Instantiate delegate with add method

            SampleDelegate<int> delegat = new SampleDelegate<int>(mathOps.Add);

            Console.WriteLine("Addition Result: " + delegat(10, 90));

            // Instantiate delegate with subtract method

            delegat = mathOps.Subtract;

            Console.WriteLine("Subtraction Result: " + delegat(10, 90));

            Console.ReadLine();

 

        }

    }

}

 

Thank you

 

References

 

1. Tutlane

2.  TutorialsTeacher

3.  MicrosoftDocumentation