C# Api 如何读取 appsettings.json？

Question

我想知道 startup.cs 是如何知道 appsettings.json 文件的，我似乎无法在 startup.cs 或 program.cs 中找到设置30=].

标准 program.cs:

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;

namespace WebApplication1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}

标准startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace WebApplication1
{
    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.AddControllers();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

我尝试将 appsettings.json 添加到控制台应用程序，但后来我不得不手动注入文件。有了这段代码：

configuration = new ConfigurationBuilder()
                .SetBasePath(Directory.GetParent(AppContext.BaseDirectory).FullName)
                .AddJsonFile("appsettings.json", false)
                .Build();

Answer 1

由于调用了 program.cs 中的 Host.CreateDefaultBuilder 方法，应用程序知道这些 appsettings 文件。

如 ASP.NET Core documentation 中所述，此方法启用一些默认行为，例如从以下位置加载应用配置：

appsettings.json.

appsettings.{Environment}.json.

User secrets when the app runs in the Development environment.

Environment variables.

Command-line arguments.

C# Api 如何读取 appsettings.json？

How does a C# Api read the appsettings.json?

c#

configuration

console-application

asp.net-core

webapi