C# Corner

ASP.NET Core: Learning the Ropes, Part 2

• 11/29/2018

Your updated Startup class file should now look like Listing 4.

Listing 4: Updated Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using VSMASPCoreApp.Models;
using VSMASPCoreApp.Repositories;

namespace VSMASPCoreApp
{
  public class Startup
  {
    public Startup(IConfiguration configuration)
    {
      Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
      services.Configure<CookiePolicyOptions>(options =>
      {
        // This lambda determines whether user consent for non-essential cookies is needed for a given request.
        options.CheckConsentNeeded = context => true;
        options.MinimumSameSitePolicy = SameSiteMode.None;
      });

      services.AddDbContext<AppDbContext>(options =>
                     options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

      services.AddTransient<IContactRepository, ContactRepository>();

      services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
      if (env.IsDevelopment())
      {
        app.UseDeveloperExceptionPage();
      }
      else
      {
        app.UseExceptionHandler("/Home/Error");
        app.UseHsts();
      }

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

      app.UseMvc(routes =>
      {
        routes.MapRoute(
          name: "default",
          template: "{controller=Home}/{action=Index}/{id?}");
      });
    }
  }
}

Next we need to add an initial EF Core migration to create the database from our model. Open up the Package Manager Console as seen in Figure 3.

In the Package Manager Console run the command "Add-Migration Initial."

You should now see a Migrations folder added to your project with a class file named Initial.cs. Now that the migration has been created it is time to create the database. Run the "Update-Database" command in the Package Manager Console. Now you should be able to run the application to verify that the database connection is indeed working. Once the application loads click on the Contact menu item and you should see an empty table with header rows on it as seen in Figure 4.

This isn't very user friendly if the user hasn't added any contacts yet in the system. Let's update the Index.cshtml Contact view to output a nice message that says "No contacts found, add a contact first." Open the Views\Contact\Index.cshtml and add in the markup from Listing 5.

Listing 5: Contact Index.cshtml

@model IEnumerable<Contact>

@if (Model.Any())
{
  <table class="table-striped table-responsive table-bordered">
    <thead>
      <tr>
        <th>First</th>
        <th>Last</th>
        <th>Email</th>
      </tr>
    </thead>
    <tbody>
      @foreach (var contact in Model)
      {
        <tr>
          <td>@contact.FirstName</td>
          <td>@contact.LastName</td>
          <td>@contact.EmailAddress</td>
        </tr>
      }
    </tbody>
  </table>
}
else
{
  <div class="alert alert-info" role="alert">
    No contacts found, add a contact first.
  </div>
}

You should now see the "No contacts found, add a contact first." message when you go to the Contact page as seen in Figure 5.

In this article I showed how to setup Entity Framework Core in an ASP.NET MVC Core application. You've seen how to implement the basic CRUD operations using EF Core. Stay tuned for the third and final article of this series where I'll show how to implement the view and controller actions needed to leverage our new contact repository.