ASP.NET Core WebAPI 6无法读取配置值，如何修复？

正在将ASP.NET Core 3.x版本的自定义JWT Token WebAPI项目迁移至ASP.NET Core WebAPI 6版本，当前遇到配置读取失败的问题，相关配置文件及代码如下：

appsettings.json 配置 #

{
  /*
The following identity settings need to be configured
before the project can be successfully executed.
*/
  "AzureAd": {
    "Instance": "https://login.microsoftonline.com/",
    "Domain": "qualified.domain.name",
    "TenantId": "22222222-2222-2222-2222-222222222222",
    "ClientId": "11111111-1111-1111-11111111111111111",
    "Scopes": "access_as_user",
    "CallbackPath": "/signin-oidc"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    },
    "ConnectionStrings": {
      "DefaultConnection": "Server=127.0.0.1;Port=5432;Database=acc200;User Id=postgres;Password=postgres;"
    }
  },
  "AllowedHosts": "*",
  "AppSettings": {
    "Key": "986ghgrgtru989ASdsaerew13434545439",
    "Issuer": "atul1234"
  }
}

开发环境配置文件（原文件名拼写错误） #

原文件名为applications.Development.json，内容如下：

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    },
    "AllowedHosts": "*",
    "AppSettings": {
      "Key": "986ghgrgtru989ASdsaerew13434545435",
      "Issuer": "atul1234"
    },
    "ConnectionStrings": {
      "DefaultConnection": "Server=127.0.0.1;Port=5432;Database=foo;User Id=postgres;Password=postgres;"
    }
  }
}

Program.cs 代码 #

using acc7.Data;
using JWTTokenPOC.Helper;
using JWTTokenPOC.Service;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Identity.Web;
using Microsoft.Identity.Web.Resource;
using System.Configuration;
using AuthenticationService = JWTTokenPOC.Service.AuthenticationService;

namespace acc7
{
    public class Program
    {
        public IConfiguration Configuration { get; }

        public Program(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public static void Main(string[] args)
        {
            var builder = WebApplication.CreateBuilder(args);
            builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme).AddMicrosoftIdentityWebApi(builder.Configuration.GetSection("AzureAd"));
            var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
            builder.Services.AddDbContext<ApplicationDbContext>(options => options.UseNpgsql("Server=127.0.0.1;Port=5432;Database=acc200;User Id=postgres;Password=postgres;"));
            builder.Services.AddControllers();

            builder.Services.Configure<AppSettings>(Configuration.GetSection("AppSettings"));

            builder.Services.AddEndpointsApiExplorer();
            builder.Services.AddSwaggerGen();

            builder.Services.AddCors();
            builder.Services.AddScoped<IUserService, UserService>();
            builder.Services.AddScoped<JWTTokenPOC.Service.IAuthenticationService, AuthenticationService>();

            var app = builder.Build();
            if (app.Environment.IsDevelopment())
            {
                app.UseSwagger();
                app.UseSwaggerUI();
            }
            app.UseHttpsRedirection();
            app.UseAuthentication();
            app.UseAuthorization();

            app.UseCors(x => x
                .AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader());

            app.UseMiddleware<JwtMiddleware>();

            app.MapControllers();
            app.Run();
        }
    }
}

错误截图 #

1. 修正配置文件命名错误 #

ASP.NET Core默认只会识别appsettings.Development.json作为开发环境配置文件，将原applications.Development.json重命名为appsettings.Development.json。

2. 修正配置文件结构错误 #

ConnectionStrings、AllowedHosts、AppSettings被错误嵌套在Logging节点下，ASP.NET Core配置系统无法正常读取，需移至根节点：

修改后的appsettings.json #

{
  "AzureAd": {
    "Instance": "https://login.microsoftonline.com/",
    "Domain": "qualified.domain.name",
    "TenantId": "22222222-2222-2222-2222-222222222222",
    "ClientId": "11111111-1111-1111-11111111111111111",
    "Scopes": "access_as_user",
    "CallbackPath": "/signin-oidc"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "ConnectionStrings": {
    "DefaultConnection": "Server=127.0.0.1;Port=5432;Database=acc200;User Id=postgres;Password=postgres;"
  },
  "AllowedHosts": "*",
  "AppSettings": {
    "Key": "986ghgrgtru989ASdsaerew13434545439",
    "Issuer": "atul1234"
  }
}

修改后的appsettings.Development.json #

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "AppSettings": {
    "Key": "986ghgrgtru989ASdsaerew13434545435",
    "Issuer": "atul1234"
  },
  "ConnectionStrings": {
    "DefaultConnection": "Server=127.0.0.1;Port=5432;Database=foo;User Id=postgres;Password=postgres;"
  }
}

3. 修正Program.cs中的配置读取错误 #

ASP.NET Core 6的静态Main方法无法访问实例属性Configuration，需直接使用builder.Configuration读取配置，同时移除多余的构造函数和System.Configuration引用：

修改后的Program.cs #

using acc7.Data;
using JWTTokenPOC.Helper;
using JWTTokenPOC.Service;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.EntityFrameworkCore;
using Microsoft.Identity.Web;
using AuthenticationService = JWTTokenPOC.Service.AuthenticationService;

namespace acc7
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var builder = WebApplication.CreateBuilder(args);
            
            builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
                .AddMicrosoftIdentityWebApi(builder.Configuration.GetSection("AzureAd"));

            // 从配置文件读取连接字符串
            var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
            builder.Services.AddDbContext<ApplicationDbContext>(options => options.UseNpgsql(connectionString));

            builder.Services.AddControllers();

            // 使用builder.Configuration读取AppSettings
            builder.Services.Configure<AppSettings>(builder.Configuration.GetSection("AppSettings"));

            builder.Services.AddEndpointsApiExplorer();
            builder.Services.AddSwaggerGen();

            builder.Services.AddCors();
            builder.Services.AddScoped<IUserService, UserService>();
            builder.Services.AddScoped<JWTTokenPOC.Service.IAuthenticationService, AuthenticationService>();

            var app = builder.Build();
            
            if (app.Environment.IsDevelopment())
            {
                app.UseSwagger();
                app.UseSwaggerUI();
            }

            app.UseHttpsRedirection();
            app.UseAuthentication();
            app.UseAuthorization();

            app.UseCors(x => x
                .AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader());

            app.UseMiddleware<JwtMiddleware>();

            app.MapControllers();
            app.Run();
        }
    }
}

4. 验证修复效果 #

重新编译运行项目后：

• 连接字符串会根据当前环境自动读取对应配置文件的值
• AppSettings配置可正常绑定到实体类
• 原编译错误会消失

内容的提问来源于stack exchange，提问作者Đỗ Như Vỹ