C# Database Examples with Entity Framework

Introduction to C# Working with Databases using Entity Framework

Entity Framework (EF) is a powerful Object-Relational Mapper (ORM) for .NET that allows developers to interact with databases using C# objects. Instead of writing complex SQL queries, EF simplifies database operations, making it easier to perform CRUD (Create, Read, Update, Delete) operations. In this article, we’ll explore three practical examples of C# working with databases using Entity Framework.

Example 1: Inserting Data into a Database

Use Case:

In a typical application, you might need to add new records to a database, such as adding a new user to a user table. This example demonstrates how to create a new user entry.

using (var context = new MyDbContext())
{
    var newUser = new User
    {
        FirstName = "John",
        LastName = "Doe",
        Email = "john.doe@example.com"
    };
    context.Users.Add(newUser);
    context.SaveChanges(); // Saves the changes to the database
}

Notes:

• Make sure you have a User class defined in your model that corresponds to the database table.
• The MyDbContext class should inherit from DbContext and have a DbSet<User> property.
• Always use SaveChanges() to persist the changes to the database.

Example 2: Querying Data from a Database

Use Case:

Retrieving data is a common requirement in applications. This example shows how to fetch a list of users from the database and display their names.

using (var context = new MyDbContext())
{
    var users = context.Users.ToList(); // Retrieves all users
    foreach (var user in users)
    {
        Console.WriteLine($"{user.FirstName} {user.LastName}"); // Displaying user names
    }
}

Notes:

• The ToList() method executes the query and retrieves the results as a list.
• Be mindful of performance; for large datasets, consider using pagination or filtering.

Example 3: Updating Data in a Database

Use Case:

When user details change, you need to update the existing records. This example illustrates how to update a user’s email address in the database.

using (var context = new MyDbContext())
{
    var user = context.Users.FirstOrDefault(u => u.Id == 1); // Find user by ID
    if (user != null)
    {
        user.Email = "john.new@example.com"; // Update email
        context.SaveChanges(); // Persist changes
    }
}

Notes:

• The FirstOrDefault method retrieves the first user if found, or returns null.
• Always check if the user exists before attempting to update to avoid null reference exceptions.

Conclusion

These examples of C# working with databases using Entity Framework showcase how straightforward it can be to manage data in your applications. Whether you are inserting, querying, or updating data, EF provides a robust framework that abstracts much of the complexity, allowing you to focus on building great applications.