Read Values from AppSettings.json File in ASP.NET Core

On the Visual Studio, create new ASP.NET Core MVC Web Application project

Select Empty Template

Click Ok button to Finish

Open Startup.cs file and add new configurations as below:

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.Extensions.DependencyInjection;

namespace LearnASPNETCoreMVCWithRealApps
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseStaticFiles();

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

        }
    }
}

Select Project and right click to select Add\New Item Menu

Select Web\ASP.NET in left side. Select App Settings File item and click Add button to Finish

In appsettings.json file and new configurations as below:

{
  "Message": "Hello World",
  "MyConfigs": {
    "Config1": "Value of Config 1",
    "Config2": "Value of Config 2",
    "Config3": "Value of Config 3"
  },
  "Logging": {
    "IncludeScopes": false,
    "Debug": {
      "LogLevel": {
        "Default": "Information"
      }
    }
  }
}

Create new folder named Controllers. In this folder, create new controller named DemoController.cs as below:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;

namespace LearnASPNETCoreMVCWithRealApps.Controllers
{
    public class DemoController : Controller
    {
        public IActionResult Index()
        {
            var builder = new ConfigurationBuilder()
                                    .SetBasePath(Directory.GetCurrentDirectory())
                                    .AddJsonFile("appsettings.json");
            var configuration = builder.Build();
            ViewBag.result1 = configuration["Message"];
            ViewBag.result2 = configuration["MyConfigs:Config1"];
            ViewBag.result3 = configuration["MyConfigs:Config2"];
            ViewBag.result4 = configuration["MyConfigs:Config3"];
            ViewBag.result5 = configuration["Logging:Debug:LogLevel:Default"];
            return View();
        }
    }
}

Create new folder named Views. In this folder, create new folder named Demo. Create new razor view named Index.cshtml as below:

@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>

    Result 1: @ViewBag.result1
    <br />
    Result 2: @ViewBag.result2
    <br />
    Result 3: @ViewBag.result3
    <br />
    Result 4: @ViewBag.result4
    <br />
    Result 5: @ViewBag.result5

</body>
</html>

Access Index action in Demo controller with following url: http://localhost:48982/Demo/Index

Output

I recommend you refer to the books below to learn more about the knowledge in this article:

Read Values from AppSettings.json File in ASP.NET Core

Create ASP.NET Core MVC Project

Add Configurations

Create AppSettings File

Create Controller

Create View

Structure of ASP.NET MVC Core Project

Run Application

References