Articles → .NET DESIGN PATTERN → Dependency Inversion Principle In C#

Dependency Inversion Principle In C#

In this article, we will discuss dependency inversion principle in C#.

What Does The Dependency Inversion Principle Say?

This principle says that

High-level modules should not depend upon the low-level module. Both modules should depend upon the abstractions.
Abstractions should not depend upon details. Details should depend upon the abstractions.

Let me try to explain about high-level and low-level modules. In the traditional application, each application is divided into presentation layer, application layer, business layer and data access layer.

Here, the presentation layer is the highest-level module and data-access layer is the lowest-level module.

Example

In this example, we will create 2 classes i.e. PresentationLayer and ApplicationLayer.

public class PresentationLayer {
  public string GetMessage() {
    ApplicationLayer applicationLayer = new ApplicationLayer();
    return applicationLayer.GetWelcomeMessage();
  }
}
public class ApplicationLayer {
  public string GetWelcomeMessage() {
    return "Welcome Karan";
  }
}

Here, the class "PresentationLayer" is directly dependent upon "ApplicationLayer".

Picture showing the traditional development method where high level module is dependent on low level module

Click to Enlarge

According to the dependency inversion principle

Create an interface.
Implement the low-level module with the interface.
Call the low-level module in the high-level module using an interface

Here is the code

public class PresentationLayer {
  IMessage _message;
  public PresentationLayer(IMessage message) {
    this._message = message;
  }

  public string GetMessage() {
    return _message.GetWelcomeMessage();
  }
}

public interface IMessage {
  string GetWelcomeMessage();
}

public class ApplicationLayer: IMessage {
  public string GetWelcomeMessage() {
    return "Welcome Karan";
  }
}

Picture showing the Dependency Inversion principle method of implementation

Click to Enlarge

Posted By -	Karan Gupta

Posted On -	Monday, December 28, 2020

Query/Feedback

Your Email Id

Subject

Query/Feedback	Characters remaining 250