Proxy Pattern in C#

Introduction

Design patterns are essential tools in a developer's toolkit, helping us create efficient, maintainable, and scalable software. One such design pattern is the Proxy Pattern, which falls under the structural design pattern category. In this article, we will explore the Proxy Pattern in C#, its purpose, implementation, and real-world use cases.

What is the Proxy Pattern?

The Proxy Pattern is a structural design pattern that provides a surrogate or placeholder for another object to control access to it. It acts as an intermediary or a wrapper around the actual object, allowing us to add extra functionality while keeping the core functionality intact. This pattern is particularly useful when we want to control access to an object or provide lazy initialization, logging, access control, or monitoring without altering the original object's code.

Key Participants in the Proxy Pattern

1. Subject: This is the interface or abstract class that defines the common interface for both the RealSubject and Proxy classes. It ensures that the Proxy and RealSubject have a common set of methods.
2. RealSubject: This is the actual object that the Proxy represents. It implements the Subject interface and performs the actual operations.
3. Proxy: The Proxy class implements the Subject interface as well but serves as an intermediary between the client and the RealSubject. It can control access to the RealSubject, add additional logic, or delay its creation until necessary.

Implementing the Proxy Pattern in C#

Let's dive into a simple example of the Proxy Pattern in C# by creating a virtual proxy for loading images.

// Subject interface
public interface IImage
{
    void Display();
}

// RealSubject
public class RealImage : IImage
{
    private string _fileName;

    public RealImage(string fileName)
    {
        _fileName = fileName;
        LoadImageFromDisk();
    }

    private void LoadImageFromDisk()
    {
        Console.WriteLine($"Loading image from {_fileName}");
    }

    public void Display()
    {
        Console.WriteLine($"Displaying image {_fileName}");
    }
}

// Proxy
public class ProxyImage : IImage
{
    private RealImage _realImage;
    private string _fileName;

    public ProxyImage(string fileName)
    {
        _fileName = fileName;
    }

    public void Display()
    {
        if (_realImage == null)
        {
            _realImage = new RealImage(_fileName);
        }
        _realImage.Display();
    }
}

In this example, RealImage represents the actual image loading logic, while ProxyImage acts as a proxy for RealImage. The ProxyImage class defers the creation of RealImage until the Display method is called.

Real-World Use Cases

1. Lazy Loading: The lazy loading of resources such as images, database connections, or network connections can be implemented using the Proxy Pattern. The real object is created only when it is needed, improving performance and resource utilization.
2. Access Control: Proxies can be used to control access to sensitive data or methods in an object. For example, you can implement access control using proxy objects that check user permissions before allowing access to certain functionality.
3. Caching: Proxies can cache the results of expensive operations, allowing subsequent requests for the same data to be served more efficiently.
4. Logging and Monitoring: Proxies can log method calls and monitor performance metrics, helping in debugging and optimization.

Conclusion

The Proxy Pattern is a valuable tool for managing object access, providing lazy loading, and adding additional functionality while maintaining the integrity of the original object. By implementing proxies, you can enhance the flexibility, security, and performance of your C# applications. Understanding this pattern and knowing when to apply it can significantly improve the architecture of your software.

Happy Learning :)