Asp.Net Core Dbcontext And Dbset Complete Guide

Step-by-Step Guide to Using DbContext and DbSet in ASP.NET Core

Step 1: Set Up Your ASP.NET Core Project

1. Open Visual Studio.
2. Create a new project:
   • Select "ASP.NET Core Web App (Model-View-Controller)".
   • Name your project (e.g., DbContextExample).
   • Choose the .NET Core version and ASP.NET Core version.
3. Click "Create".

Step 2: Install Entity Framework Core

1. Right-click on your project in Solution Explorer and select Manage NuGet Packages.
2. Search for Microsoft.EntityFrameworkCore.SqlServer and install it.
3. Install Microsoft.EntityFrameworkCore.Tools for Entity Framework Core tools.

Step 3: Create a Model

Create a new class in a new file named Book.cs:

namespace DbContextExample.Models
{
    public class Book
    {
        public int BookId { get; set; }
        public string Title { get; set; }
        public string Author { get; set; }
    }
}

Step 4: Create a DbContext

Create a new class named AppDbContext.cs:

using Microsoft.EntityFrameworkCore;
using DbContextExample.Models;

namespace DbContextExample.Data
{
    public class AppDbContext : DbContext
    {
        public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)
        {
        }

        public DbSet<Book> Books { get; set; }
    }
}

Step 5: Configure DbContext in Startup.cs

Modify the Startup.cs file to register the DbContext with the dependency injection container:

using Microsoft.EntityFrameworkCore;
using DbContextExample.Data;

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        // Configure DbContext
        services.AddDbContext<AppDbContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

        services.AddControllersWithViews();
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            app.UseHsts();
        }

        app.UseHttpsRedirection();
        app.UseStaticFiles();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=Home}/{action=Index}/{id?}");
        });
    }

    public IConfiguration Configuration { get; }
}

Step 6: Add Connection String in appsettings.json

Add a connection string in appsettings.json:

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=DbContextExampleDB;Trusted_Connection=True;MultipleActiveResultSets=true"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*"
}

Step 7: Create a Migration

Open the Package Manager Console in Visual Studio and run the following command to create a migration:

Add-Migration InitialCreate

Step 8: Apply the Migration

Run the following command to apply the migration and create the database:

Update-Database

Step 9: Create a Controller

Add a new controller named BooksController.cs:

using System.Linq;
using Microsoft.AspNetCore.Mvc;
using DbContextExample.Data;
using DbContextExample.Models;

namespace DbContextExample.Controllers
{
    public class BooksController : Controller
    {
        private readonly AppDbContext _context;

        public BooksController(AppDbContext context)
        {
            _context = context;
        }

        public IActionResult Index()
        {
            var books = _context.Books.ToList();
            return View(books);
        }

        public IActionResult Create()
        {
            return View();
        }

        [HttpPost]
        public IActionResult Create(Book book)
        {
            if (ModelState.IsValid)
            {
                _context.Add(book);
                _context.SaveChanges();
                return RedirectToAction(nameof(Index));
            }
            return View(book);
        }
    }
}

Step 10: Create Views for the Books Controller

Create a new folder named Books inside the Views folder. Then, create the following views:

1. Index.cshtml:

@model IEnumerable<DbContextExample.Models.Book>

<h2>Books</h2>

<p>
    <a asp-action="Create">Create New</a>
</p>
<table class="table">
    <thead>
        <tr>
            <th>
                @Html.DisplayNameFor(model => model.Title)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Author)
            </th>
            <th></th>
        </tr>
    </thead>
    <tbody>
@foreach (var item in Model) {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.Title)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Author)
            </td>
            <td>
                <a asp-action="Edit" asp-route-id="@item.BookId">Edit</a> |
                <a asp-action="Details" asp-route-id="@item.BookId">Details</a> |
                <a asp-action="Delete" asp-route-id="@item.BookId">Delete</a>
            </td>
        </tr>
}
    </tbody>
</table>

2. Create.cshtml:

@model DbContextExample.Models.Book

<h2>Create</h2>

<form asp-action="Create">
    <div class="form-group">
        <label asp-for="Title" class="control-label"></label>
        <input asp-for="Title" class="form-control" />
        <span asp-validation-for="Title" class="text-danger"></span>
    </div>
    <div class="form-group">
        <label asp-for="Author" class="control-label"></label>
        <input asp-for="Author" class="form-control" />
        <span asp-validation-for="Author" class="text-danger"></span>
    </div>
    <div class="form-group">
        <input type="submit" value="Create" class="btn btn-primary" />
    </div>
</form>

Step 11: Run the Application

1. Press F5 or click "Start" to run the application.
2. Navigate to /Books to see the index page.
3. You can create new books and see them listed.

Summary

In this example, you learned how to set up an ASP.NET Core project, configure Entity Framework Core, create a DbContext and DbSet, register the DbContext with the dependency injection container, create a controller and views, and perform basic CRUD operations.