This content originally appeared on DEV Community and was authored by Saoud
Database Schema and Relationship Types
Terminology
- Database schema: The structure that represents the way the database is built. It defines how data is stored in the database tables and how the relations among tables are associated.
- One-to-one Relationship: Two tables have a one-to-one relationship when a row on one table is related to only one row on the other table.
- One-to-many relationship: Two tables share a one-to-many relationship when a single row on one table can be related to many rows on another table.
- Many-to-many relationship: Two tables share a many-to-many relationship when each row on each table can have many rows on the other table. This relationship requires use of a join table.
- Join table: Used to manage all possible relationships in a many-to-many relationship, a join table contains individual entries.
Configuration for Entity Framework Core
ToDoList.csproj
<Project Sdk="Microsoft.NET.Sdk.Web">
<PropertyGroup>
<TargetFramework>net5.0</TargetFramework>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="Microsoft.EntityFrameworkCore" Version="5.0.0" />
<PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="5.0.0-alpha.2" />
</ItemGroup>
</Project>
appsettings.json
{
"ConnectionStrings": {
"DefaultConnection": "Server=localhost;Port=3306;database=to_do_list;uid=root;pwd=[YOUR-PASSWORD-HERE];"
}
}
Make sure your appsettings.json file is in your .gitignore!
Startup.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using ToDoList.Models;
namespace ToDoList
{
public class Startup
{
public Startup(IWebHostEnvironment env)
{
var builder = new ConfigurationBuilder()
.SetBasePath(env.ContentRootPath)
.AddJsonFile("appsettings.json");
Configuration = builder.Build();
}
public IConfigurationRoot Configuration { get; set; }
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
services.AddEntityFrameworkMySql()
.AddDbContext<ToDoListContext>(options => options
.UseMySql(Configuration["ConnectionStrings:DefaultConnection"], ServerVersion.AutoDetect(Configuration["ConnectionStrings:DefaultConnection"])));
}
public void Configure(IApplicationBuilder app)
{
app.UseDeveloperExceptionPage();
app.UseRouting();
app.UseEndpoints(routes =>
{
routes.MapControllerRoute("default", "{controller=Home}/{action=Index}/{id?}");
});
app.UseStaticFiles();
app.Run(async (context) =>
{
await context.Response.WriteAsync("Hello World!");
});
}
}
}
Program.cs
using System.IO;
using Microsoft.AspNetCore.Hosting;
namespace ToDoList
{
public class Program
{
public static void Main(string[] args)
{
var host = new WebHostBuilder()
.UseKestrel()
.UseContentRoot(Directory.GetCurrentDirectory())
.UseIISIntegration()
.UseStartup<Startup>()
.Build();
host.Run();
}
}
}
Models/ToDoListContext.cs
using Microsoft.EntityFrameworkCore;
namespace ToDoList.Models
{
public class ToDoListContext : DbContext
{
public DbSet<Item> Items { get; set; }
public ToDoListContext(DbContextOptions options) : base(options) { }
}
}
EF Core with an Existing Database
Models/Item.cs
namespace ToDoList.Models
{
public class Item
{
public int ItemId { get; set; }
public string Description { get; set; }
}
}
Controllers/ItemsController.cs
using Microsoft.AspNetCore.Mvc;
using ToDoList.Models;
using System.Collections.Generic;
using System.Linq;
namespace ToDoList.Controllers
{
public class ItemsController : Controller
{
private readonly ToDoListContext _db;
public ItemsController(ToDoListContext db)
{
_db = db;
}
public ActionResult Index()
{
List<Item> model = _db.Items.ToList();
return View(model);
}
}
}
Controllers/HomeController.cs
using Microsoft.AspNetCore.Mvc;
namespace ToDoList.Controllers
{
public class HomeController : Controller
{
[HttpGet("/")]
public ActionResult Index()
{
return View();
}
}
}
Views/Items/Index.cshtml
@{
Layout = "_Layout";
}
@using ToDoList.Models;
<h1>Items</h1>
@if (@Model.Count == 0)
{
<h3>No items have been added yet!</h3>
}
@foreach (Item item in Model)
{
<li>@item.Description</li>
}
Create and Read with EF Core
Controllers/ItemsController.cs
using Microsoft.AspNetCore.Mvc;
using ToDoList.Models;
using System.Collections.Generic;
using System.Linq;
namespace ToDoList.Controllers
{
public class ItemsController : Controller
{
private readonly ToDoListContext _db;
public ItemsController(ToDoListContext db)
{
_db = db;
}
public ActionResult Index()
{
List<Item> model = _db.Items.ToList();
return View(model);
}
public ActionResult Create()
{
return View();
}
[HttpPost]
public ActionResult Create(Item item)
{
_db.Items.Add(item);
_db.SaveChanges();
return RedirectToAction("Index");
}
}
}
This content originally appeared on DEV Community and was authored by Saoud
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Saoud | Sciencx (2021-05-09T22:14:43+00:00) Database Basics. Retrieved from https://www.scien.cx/2021/05/09/database-basics/
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HARVARDSaoud | Sciencx Sunday May 9, 2021 » Database Basics., viewed ,<https://www.scien.cx/2021/05/09/database-basics/>
VANCOUVERSaoud | Sciencx - » Database Basics. [Internet]. [Accessed ]. Available from: https://www.scien.cx/2021/05/09/database-basics/
CHICAGO" » Database Basics." Saoud | Sciencx - Accessed . https://www.scien.cx/2021/05/09/database-basics/
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