Proxy

Proxy Pattern

Intent

Provide a surrogate or placeholder for another object to control access to it.

Problem

You need to control access to an object, add functionality before/after accessing it, or delay its creation until actually needed.

Solution

The Proxy pattern creates a proxy object that has the same interface as the real object, allowing it to control access and add additional functionality.

When to Use

• Lazy initialization (virtual proxy) - defer object creation until needed
• Access control (protection proxy) - control access based on permissions
• Local execution of remote service (remote proxy)
• Logging requests (logging proxy)
• Caching request results (caching proxy)
• Smart reference - additional actions when an object is accessed

C# Implementation

See the Program.cs file for an image proxy demonstrating lazy loading and caching.

Pros

• Can control the service object without clients knowing about it
• Can manage lifecycle of service object
• Proxy works even if service isn't ready or available
• Open/Closed Principle - introduce new proxies without changing service or clients

Cons

• Code may become more complicated with many new classes
• Response from service might get delayed