How to create a generic class and method in C#?

You can create an instance of generic classes by specifying an actual type in angle brackets. The following creates an instance of the generic class DataStore.

DataStore<string> store = new DataStore<string>();

Above, we specified the string type in the angle brackets while creating an instance. So, T will be replaced with a string type wherever T is used in the entire class at compile-time. Therefore, the type of Data property would be a string.

You can assign a string value to the Data property. Trying to assign values other than string will result in a compile-time error.

DataStore<string> store = new DataStore<string>();
store.Data = 'Hello World!';
//store.Data = 123; //compile-time error

You can specify the different data types for different objects, as shown below.

DataStore<string> strStore = new DataStore<string>();
strStore.Data = 'Hello World!';
//strStore.Data = 123; // compile-time error

DataStore<int> intStore = new DataStore<int>();
intStore.Data = 100;
//intStore.Data = 'Hello World!'; // compile-time error

KeyValuePair<int, string> kvp1 = new KeyValuePair<int, string>();
kvp1.Key = 100;
kvp1.Value = 'Hundred';

KeyValuePair<string, string> kvp2 = new KeyValuePair<string, string>();
kvp2.Key = 'IT';
kvp2.Value = 'Information Technology';

We can create a generic class in C# that can be used with objects of any type. This type of class is called Generic Class. We can also create a generic method like a generic class which can be called with any type of argument. The compiler handles each method based on the arguments passed to the generic method.

Class class-name<T>

 {

      access-modifier datatype method-name(){

      }

      access-modifier T method-name(){

      }

 }

using System;

//Generic Class

class Genericdemo <T>

{

 //Generic property

 private T[] _data = new T[10];

    public void AddOrUpdate(int index, T item)

    {

        if(index >= 0 && index < 10)

            _data[index] = item;

    }

  //Generic Method

    public T GetData(int index)

    {

        if(index >= 0 && index < 10)

            return _data[index];

    return default(T);

    }

}

public class Program

{

 public static void Main()

 {

  Genericdemo<string> gd= new Genericdemo<string>();  //Generic class object

  gd.AddOrUpdate(0,'Ashu');

  gd.AddOrUpdate(1,'Anupam');

  gd.AddOrUpdate(2,'Manish');

  gd.AddOrUpdate(3,'Sunny');

  gd.AddOrUpdate(4,'Shyam');

  for(int i=0;i<7;i++)  

   Console.WriteLine(gd.GetData(i));  //Generic Method calling

 }

}

Ashu

Anupam

Manish

Sunny

Shyam