Dependency Injection In .Net Core With Example

Design Pattern 

A design pattern in C# (or any other programming language) is a reusable solution to a common problem that occurs in software development. Design patterns provide a structured approach to solving these problems, and they are widely recognized as best practices in the software development community.

There are several types of design patterns, including creational patterns, structural patterns, and behavioral patterns. Some of the most well-known design patterns include the Singleton, Factory, Observer, Decorator, and Command patterns.

Design patterns are not specific to any particular programming language and can be implemented in any language, including C#. In C#, you can implement design patterns by using various language features such as classes, interfaces, delegates, and lambdas.

Using design patterns can help to improve the structure, maintainability, and scalability of your code, and they can also help to make your code more readable and understandable to others. However, it's important to use design patterns appropriately and not to overuse them, as this can lead to code that is difficult to understand and maintain.

Dependency Injection

Dependency Injection (DI) is a design pattern that is widely used in software development to achieve a high level of decoupling between different components. The main idea behind this pattern is to manage the dependencies between components in a more efficient and flexible manner. In other words, it is a technique for providing objects with their required dependencies instead of tightly coupling them.

.NET Core is an open-source, cross-platform framework developed by Microsoft that supports multiple programming languages. The framework has built-in support for dependency injection, which makes it easy to implement DI in your applications.

Before diving into how to implement DI in .NET Core, let's understand the concept of DI.

What is Dependency Injection?

Dependency Injection is a technique where objects are provided with their dependencies, either through constructors, properties, or methods. This allows the objects to be more flexible and reusable, as they do not rely on hard-coded dependencies.

For example, consider an application that contains a class named "OrderProcessor". This class requires an instance of a "PaymentGateway" class to process the payment for an order. Without DI, the "OrderProcessor" class would have to create an instance of the "PaymentGateway" class within itself. However, this tight coupling between the two classes makes it difficult to change the payment gateway in the future or to test the "OrderProcessor" class.

With DI, the "OrderProcessor" class can receive the "PaymentGateway" class as a dependency, either through its constructor or through a property. This makes it easier to change the payment gateway in the future or to test the "OrderProcessor" class, as you can simply provide a different implementation of the "PaymentGateway" class.

How to implement Dependency Injection in .NET Core?

.NET Core provides built-in support for dependency injection, which makes it easy to implement DI in your applications. To implement DI in .NET Core, you can use the built-in IoC container, which is a component that manages the creation and lifetime of objects.

Here is an example of how to implement DI in a .NET Core application,

1. Create a class library project and define the interfaces and classes that you want to inject. For example, let's create an interface named "IPaymentGateway" and a class named "PaymentGateway".

public interface IPaymentGateway {
    void ProcessPayment();
}
public class PaymentGateway: IPaymentGateway {
    public void ProcessPayment() {
        // Implementation of the payment gateway.
    }
}

2. In the Startup class of your .NET Core application, configure the IoC container to use the implementation of the "IPaymentGateway" interface.

public class Startup {
    public void ConfigureServices(IServiceCollection services) {
        services.AddTransient < IPaymentGateway, PaymentGateway > ();
    }
    // Rest of the Startup class.
}

3. Inject the "IPaymentGateway" interface into your classes by either using a constructor or a property. For example, let's create a class named "OrderProcessor".

public class OrderProcessor {
    private readonly IPaymentGateway _paymentGateway;
    public OrderProcessor(IPaymentGateway paymentGateway) {
        // Implementation part
    }
}

In summary, design patterns are reusable solutions to common problems in software development that provide a structured approach to solving these problems.

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