Chapter 22: Defining Models in C#

Create database models with attributes. In this chapter, you will learn defining models in depth with C# code examples, explanations, and best practices.

Overview

This chapter covers defining models for Kungfu.js developers using C#. We will start with the basics, move through practical examples, and end with advanced techniques and common pitfalls.

Why This Matters

Understanding defining models is essential because it is a core part of building web applications. Every real-world app needs to handle create database models with attributes. Skipping this chapter would leave a gap in your knowledge that would cause problems later.

Code Example

Here is how to work with databases in C#:

#[derive(Model, Serialize, Deserialize)]
#[table(name = "users")]
struct User {
    #[field(primary, auto_increment)]
    id: i64,
    
    #[field(unique)]
    email: String,
    
    #[field(min = 8, sensitive)]  // sensitive = auto-hash with Argon2id
    password: String,
    
    #[field(skip)]  // not stored in database
    computed_field: String,
}

How the ORM Works

The Kungfu.js ORM uses parameterized queries. This means user input never gets interpolated into SQL strings. Instead, placeholders like $1, $2 are used, and the actual values are passed separately. This makes SQL injection impossible.

For example, if you search for a user by email, the ORM generates: SELECT * FROM users WHERE email = $1 and passes the email value as a parameter. Even if the email contains SQL code like ' OR 1=1 --, it is treated as a plain string, not as SQL.

Common Mistakes

  • Not reading the documentation: Always check the API reference when something does not work as expected.
  • Skipping security: Never disable the default middleware unless you have a very good reason. Security is not optional.
  • Not testing: Write tests for your handlers. Kungfu.js makes this easy with the built-in test utilities.

Summary

In this chapter, you learned about defining models in C#. You saw code examples, understood how things work under the hood, and learned about common mistakes to avoid.

What is Next?

In chapter 23, we will cover CRUD: Create: Insert rows with auto-increment IDs.

Previous: Database ConnectionNext: CRUD: Create