ShortCircuitingApp

Example of console application that demonstrates short-circuiting .NET C#

Table of Contents

• Overview
• Project Structure
• Short-Circuiting Explanation
• Correct vs Incorrect Implementations
  • Correct User Validation
  • Incorrect User Validation
• How to Run
• Contributing
• License
• Blog

Overview

This project demonstrates the concept of short-circuiting in C# and how it applies to conditional checks in user validation scenario. It compares a correct implementation of user validation with an incorrect one, showing how improper ordering of conditions can lead to runtime exceptions like NullReferenceException.

Project Structure

ShortCircuitingApp/
├── Models/
│   └── User.cs
├── Repository/
│   └── UserRepository.cs
├── Service/
│   └── UserService.cs
├── Program.cs

• User: Defines the user model.
• UserRepository: Contains the mock database and method to fetch users.
• UserService: Contains the business logic for validating users, including the correct and incorrect implementations.
• Program: Entry point of the application where the service is used and tested.

Short-Circuiting Explanation

Short-circuiting refers to the evaluation of logical expressions where if the result is already determined the remaining conditions are not evaluated.

In C#, logical && and || operators are short-circuiting:

• && (AND): If the first condition is false, the second condition is not evaluated.
• || (OR): If the first condition is true, the second condition is not evaluated. In this project, we use short-circuiting to demonstrate how to correctly validate user objects

Correct vs Incorrect Implementations

Correct User Validation

The correct implementation of user validation ensures that all conditions are checked in a safe order, preventing potential exceptions. This method first checks if the user object is null before accessing properties.

public (string? UserJson, string? Message) GetUser(int userId)
{
    var user = _userRepository.GetUserById(userId);
    if (user != null && user.IsActive)
    {
        string userJson = JsonSerializer.Serialize(user);
        return (userJson, "Valid user found");
    }
    else
    {
        return ("No user", "Valid user not found");
    }
}

Incorrect User Validation

In this example the method improperly checks user.IsActive before confirming if user is null. This can cause a NullReferenceException if user is null.

public (string? UserJson, string? Message) GetUserBadImplementation(int userId)
{
    var user = _userRepository.GetUserById(userId);
    if (user.IsActive && user != null)
    {
        string userJson = JsonSerializer.Serialize(user);
        return (userJson, "Valid user found");
    }
    else
    {
        return ("No user", "Valid user not found");
    }
}

How to Run

1. Clone the repository:

git clone https://github.com/denisalibasic/ShortCircuitingApp
cd ShortCircuitingApp

2. Run the application:

dotnet run

3. Enter a user ID when prompted to test both the correct and incorrect implementations of user validation

Contributing

Contributions are welcome! Feel free to submit a pull request or open an issue if you encounter any bugs or have suggestions for improvements.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Blog

Link to related blog post: Cloud codeblock