Introduction

Recently, I had an issue with migration in .NET using entity framework core. I kept getting error reports on the NuGet package manager console. This article would provide a detailed explanation of how I resolved this problem. I am Fredrick Chukwuma, a .NET Developer that is result and process-oriented.

What Is Entity Framework?

Entity Framework is a modern object-relation mapper that lets you build a clean, portable, and high-level data access layer with .NET (C#) across a variety of databases. It makes programming easier and faster.

Prerequisites

To follow along, ensure you have the following:

• Visual studio

• Familiarity with .NET and the Entity framework

• Installed .NET locally

• A SQL Server or Azure SQL database

Step 1: Create a new ASP.NETCore Web API Project

Open visual studio, click on new project, select ASP.NETCore Web API and configure the project

Step 2: Create a Model

Create a new folder named "Models" in the root directory. Then create a new c# class named "Student.cs" and add properties as done below:

 public class Student
    {
        public Guid Id { get; set; }
        public string? FirstName { get; set; }
        public string? LastName { get; set; }
        public string? Department { get; set; }

    }

Note: The question mark at the end of each property data type is to make it nullable.

Step 3: Include connection string in appsettings.json file

Open the appsettings.json file then add the line below. Replace the server name with the name of your server

"ConnectionStrings": { "DefaultConnection": "Server=Your-ServerName\\SQLEXPRESS;Database=StudentApp;Trusted_Connection=True;TrustServerCertificate=True" }
}

Step 4: Create and Register your App DbContext

Create a folder named Data in your root directory then create an AppDbContext Class in the Data folder and inherit from the DbContext class (The DbContext class is an in-built class in .NET). Also, create a field in this class as shown below

public class ApplicationDbContext : DbContext
    {

            public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
            {

            }

            public DbSet<Student> Students { get; set; }

    }

Register a service in the program class as shown below:

builder.Services.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

Step 5: Install Entity Framework Core Packages

On the menu bar, click on tools, select NuGet package manager , then select Manage NuGet Packages For solution . Click browse and install the following packages:

• Microsoft.EntityFramewrokCore

• Microsoft.EntityFramewrokCore.SqlServer

• Microsoft.EntityFramewrokCore.Tools

Note: Ensure you install the version of each package that relates to the .NET Framework installed on your system.

Step 6: Add Migration

On the menu bar, click on tools, select NuGet package manager, then select Package Manager console.
On the console type "add-migration" space "AddStudentTable" (this is the name of the migration, you can use any name of your choice) then press enter.

When, the build is done, on the Package Manager console, type "update-database" then press enter.

Once you see this, you're done! Congrats! You understand migrations in .NET using Entity Framework core!

Conclusion

As easy as these steps seem, I didn't find it funny a while ago. I encountered a serious issue because I couldn't get the accurate name of my local server and hence my "connection string" was faulty. I also had little idea of the AppDbContext class I was suppose to create to enable a smooth migration. I kept seeing error messages on my Package Manager console, but I figured it out in the end.
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