Strategy Pattern In USSD C#

Implementing the Strategy Pattern in USSD Banking Applications: A C# Approach
Introduction
In the complex world of mobile banking, particularly with USSD (Unstructured Supplementary Service Data) applications, flexibility and extensibility are crucial. The Strategy Pattern emerges as a powerful design pattern that allows dynamic algorithm selection and provides a robust solution for handling various banking operations.
Understanding the Strategy Pattern
The Strategy Pattern is a behavioral design pattern that enables selecting an algorithm at runtime. In the context of a USSD banking application, this means we can dynamically choose different strategies for various banking operations without modifying the core application logic.
Real-world Scenario: USSD Banking Operations
Consider a banking USSD application that needs to support multiple types of transactions:

Account Balance Inquiry
Fund Transfer
Mobile Money Transfer
Bill Payments

// Strategy Interface
public interface ITransactionStrategy
{
    bool ValidateTransaction(TransactionRequest request);
    TransactionResult ProcessTransaction(TransactionRequest request);
}

// Concrete Strategies
public class BalanceInquiryStrategy : ITransactionStrategy
{
    public bool ValidateTransaction(TransactionRequest request)
    {
        // Validate balance inquiry specifics
        return request.AccountType != null;
    }

    public TransactionResult ProcessTransaction(TransactionRequest request)
    {
        // Retrieve and return account balance
        decimal balance = GetAccountBalance(request.AccountNumber);
        return new TransactionResult 
        { 
            Success = true, 
            Message = $"Your balance is: {balance}" 
        };
    }
}

public class FundTransferStrategy : ITransactionStrategy
{
    public bool ValidateTransaction(TransactionRequest request)
    {
        // Validate fund transfer specifics
        return request.SourceAccount != null 
               && request.DestinationAccount != null 
               && request.Amount > 0;
    }

    public TransactionResult ProcessTransaction(TransactionRequest request)
    {
        // Perform fund transfer logic
        bool transferSuccessful = ExecuteFundTransfer(request);
        return new TransactionResult 
        { 
            Success = transferSuccessful, 
            Message = transferSuccessful 
                ? "Transfer successful" 
                : "Transfer failed" 
        };
    }
}

// Transaction Context
public class TransactionContext
{
    private ITransactionStrategy _strategy;

    public void SetStrategy(ITransactionStrategy strategy)
    {
        _strategy = strategy;
    }

    public TransactionResult ExecuteTransaction(TransactionRequest request)
    {
        if (_strategy == null)
        {
            return new TransactionResult 
            { 
                Success = false, 
                Message = "No transaction strategy defined" 
            };
        }

        if (!_strategy.ValidateTransaction(request))
        {
            return new TransactionResult 
            { 
                Success = false, 
                Message = "Transaction validation failed" 
            };
        }

        return _strategy.ProcessTransaction(request);
    }
}

// Usage in USSD Application
public class UssdBankingService
{
    private readonly TransactionContext _transactionContext;

    public UssdBankingService()
    {
        _transactionContext = new TransactionContext();
    }

    public TransactionResult HandleUssdRequest(string ussdCode, TransactionRequest request)
    {
        switch (ussdCode)
        {
            case "*123#":
                _transactionContext.SetStrategy(new BalanceInquiryStrategy());
                break;
            case "*124#":
                _transactionContext.SetStrategy(new FundTransferStrategy());
                break;
            // Additional strategies can be easily added
        }

        return _transactionContext.ExecuteTransaction(request);
    }
}

Benefits in USSD Banking Context

Flexibility: Easily add new transaction types without modifying existing code
Maintainability: Each strategy is self-contained and can be modified independently
Runtime Strategy Selection: Choose appropriate transaction strategy dynamically
Separation of Concerns: Each transaction type has its own validation and processing logic

Advanced Considerations

Implement comprehensive error handling
Add logging for each transaction strategy
Create unit tests for individual strategies
Implement caching mechanisms for performance optimization

Conclusion
The Strategy Pattern provides a robust, flexible approach to handling diverse transaction types in USSD banking applications. By decoupling algorithm implementation from the context, we create a scalable and maintainable solution that can easily adapt to changing business requirements.
Key Takeaways

Strategy Pattern enables dynamic algorithm selection
Each banking operation can be a separate, independent strategy
Easily extensible for new transaction types
Improves code maintainability and readability