State Pattern in C# – Real-Time Example (Behavior Based on State)

What is State Pattern?

The State Pattern is a behavioral design pattern where an object changes its behavior when its internal state changes.

👉 The object behaves differently depending on its current state.

It is similar to a finite state machine.

Why Use State Pattern?

  • Remove large if-else/switch statements
  • Organize state-specific behavior
  • Improve maintainability
  • Make state transitions cleaner
  • Follow Open/Closed Principle

Real-Time Scenario

Order Processing System:

  • Pending
  • Paid
  • Shipped
  • Delivered
  • Cancelled

👉 Order behavior changes based on current status.

Real-Time Example – Order State Workflow

Step 1: State Interface


public interface IOrderState
{
    void Handle();
}

Step 2: Concrete States

Pending State


public class PendingState : IOrderState
{
    public void Handle()
    {
        Console.WriteLine("Order is Pending");
    }
}

Paid State


public class PaidState : IOrderState
{
    public void Handle()
    {
        Console.WriteLine("Order is Paid");
    }
}

Shipped State


public class ShippedState : IOrderState
{
    public void Handle()
    {
        Console.WriteLine("Order is Shipped");
    }
}

Step 3: Context Class


public class OrderContext
{
    private IOrderState _state;

    public void SetState(IOrderState state)
    {
        _state = state;
    }

    public void Process()
    {
        _state.Handle();
    }
}

Usage Example


var order = new OrderContext();

order.SetState(new PendingState());
order.Process();

order.SetState(new PaidState());
order.Process();

order.SetState(new ShippedState());
order.Process();

Output


Order is Pending
Order is Paid
Order is Shipped

Key Concept

Instead of:


if(status == "Pending")
{
}
else if(status == "Paid")
{
}
else if(status == "Shipped")
{
}

We do:


SetState(new PaidState());

👉 Behavior changes dynamically.

Diagram Understanding


OrderContext
     ↓
IOrderState
     ↓
-------------------------
PendingState
PaidState
ShippedState

👉 Each state has separate behavior.

Advantages

  • ✔ Removes complex conditions
  • ✔ Cleaner state management
  • ✔ Easier to extend new states
  • ✔ Better maintainability
  • ✔ Encapsulates state behavior

Disadvantages

  • ✖ More classes
  • ✖ Can increase complexity
  • ✖ State transitions need careful management

When to Use

Use State Pattern when:

  • Object behavior changes based on state
  • Large conditional logic exists
  • Workflow/state transitions are complex
  • States change dynamically

Real Project Mapping (.NET + Angular)

Feature Usage
Order workflow State
Payment lifecycle State
Ticket status State
User authentication flow State
Document approval workflow State

ASP.NET Core Real Example

Authentication State:

  • Unauthenticated
  • Authenticated
  • Locked
  • Expired

👉 User behavior changes by state.

Advanced Example – Payment System


Pending
   ↓
Processing
   ↓
Success / Failed

👉 Each state handles logic differently.

State vs Strategy

State Strategy
Changes behavior by internal state Changes behavior by selected algorithm
State transitions important Algorithms independent
Workflow-oriented Behavior-oriented

Pro Tip

State Pattern works well with:

  • Workflow engines
  • Finite state machines
  • CQRS workflows
  • Event-driven systems
  • Saga orchestration

Summary

State Pattern helps you:

  • Manage state-based behavior cleanly
  • Remove large conditional blocks
  • Build scalable workflows

👉 Perfect for:

  • Order systems
  • Payment processing
  • Approval workflows
  • Authentication systems

Comments

Post a Comment

Popular posts from this blog

Promises in Angular

🚀 Promises in Angular – The Complete Beginner’s Guide (with Examples) 📘 Introduction In modern Angular development, handling asynchronous operations is essential. Whether you're fetching data from an API, loading files, or wrapping browser-native APIs, Promises offer a clean and readable way to deal with one-time asynchronous operations. This guide explains: What Promises are How they compare with Observables Real-world examples using .then() and async/await When to use Promises vs Observables in Angular 📚 Table of Contents 🔍 What is a Promise? 🔁 Promise Lifecycle ✨ Key Features 📌 Syntax 💻 Example 1: Fetch 💻 Example 2: setTimeout 📊 Promises vs Observables 🎯 When to Use Promises 📦 Angular Service Example 🔄 Observable vs Promise ❓ FAQ ✅ Summary 🔍 What is a Promise? A Promise is a JavaScript object that represents the eventual success (fulfilled) or failure (rejected) of an asynchronous operation. 📌 Com...
Read more

Debouncing & Throttling in RxJS: Optimizing API Calls and User Interactions

RxJS Debounce vs Throttle in Angular – Best Practices & Examples What is RxJS — quick primer RxJS (Reactive Extensions for JavaScript) provides Observables and operators to model and manipulate streams of asynchronous events — from keystrokes and HTTP requests to timers and WebSocket messages. 💡 Why this matters: Operators like debounceTime and throttleTime help you control event frequency, reducing wasted CPU and network work while improving UX. 1. Debouncing — emit after silence Debouncing delays emitting a value until a specified period of inactivity. It's best for typeahead inputs where only the final value after the user stops typing is relevant. Live search example (production-ready) // search.component.ts import { Component, OnDestroy } from '@angular/core'; import { FormControl } from '@angular/forms'; import { Subject } from 'rxjs'; import { debounc...
Read more

Csharp Coding - Session

Image
✅ Reverse String Array using System; public class Program { public static void Main() { ReverseStringArray (); } public static void ReverseStringArray() { string[] str = { "priya", "Sai" }; int length = str.Length; for (int i = 0, j = length - 1; i < j; i++, j--) { string temp = str[i]; str[i] = str[j]; str[j] = temp; } Console.WriteLine(string.Join(", ", str)); // Output: Sai, priya } } Output: Sai, priya ✅ Reverse String Array + Each Word using System; public class Program { public static void Main() { ReverseStringArray(); } public static void ReverseStringArray() { string[] str = { "priya", "Sai" }; // Step 1: Reverse the array string[] reversedArray = ReverseArray (str); // Step 2: Reverse e...
Read more