依赖注入之IConfiguration 访问appSetting.json

（1）创建NET6 Webapi

(2)appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "AppSettings": {
    //单库
    "ConnectionString": "Server=cnps-mis-yfw;User Id=sa;Password=123;Database=northwind;"
  },
  "DBS": [
    //多库(数组)
    {
      "dbid": "0",
      "conn": "Server=cnps-mis-yfw;User Id=sa;Password=123;Database=northwind1;"
    },
    {

      "dbid": "1",
      "conn": "Server=cnps-mis-yfw;User Id=sa;Password=456;Database=northwind2;"
    },
    {
      "dbid": "2",
      "conn": "Server=cnps-mis-yfw;User Id=sa;Password=789;Database=northwind3;"
    }
  ],
  "Settings": {
    //对象
    "Name": "test123",
    "IsValid": true,
    "Counter": 123
  },
  "MulConn": {
    "code": "200",
    "msg": "ok",
    "data": [
      {
        "dbid": "0",
        "conn": "Server=cnps-mis-yfw;User Id=sa;Password=123;Database=northwind1;"
      },
      {
        "dbid": "1",
        "conn": "Server=cnps-mis-yfw;User Id=sa;Password=456;Database=northwind2;"
      },
      {
        "dbid": "2",
        "conn": "Server=cnps-mis-yfw;User Id=sa;Password=789;Database=northwind3;"
      }
    ]
  }
}

(3)program.cs

IConfiguration configuration = new ConfigurationBuilder()
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .Build();

var builder = WebApplication.CreateBuilder(args);

//builder.Services.AddSingleton(configuration);
//或
builder.Services.AddSingleton<IConfiguration>(configuration);
// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

(4)UserController.cs

//using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
//using Microsoft.Extensions.Configuration;
//using static System.Collections.Specialized.BitVector32;
//using Microsoft.Extensions.Configuration.Json;
//using static webapi02.Controllers.UserController;

namespace webapi02.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class UserController : ControllerBase
    {
        private readonly IConfiguration _configuration;
        public UserController(IConfiguration config)
        {
            _configuration = config;
        }

        [HttpGet("[action]")]
        public IActionResult SayHello()
        {
            //(01)
            string? connstr = _configuration["AppSettings:ConnectionString"];
            string? connstr2 = _configuration.GetValue<string>("AppSettings:ConnectionString");
            //结果：Server=cnps-mis-yfw;User Id=sa;Password=123;Database=northwind;
            //(02)           
            List<dbconfig> list1 = new List<dbconfig>();
            _configuration.Bind(string.Join(":", new string[] { "DBS" }), list1);
            //或
            List<dbconfig> list2 = new List<dbconfig>();           
            _configuration.Bind(string.Join(":", new string[] { "MulConn", "data" }), list2);
          
            //(03)
            var list3 = new List<dbconfig>();          
            _configuration.GetSection("MulConn:data").Bind(list3);
            //或
            var list4 = new List<dbconfig>();
            _configuration.GetSection("MulConn").Bind("data",list4);
            //(04)
            var settings = new Settings();           
            _configuration.GetSection("Settings").Bind(settings);

            return new JsonResult(list1);
            //return new JsonResult(settings);
            //list1~list4结果：
            //[
            //  {
            //    "dbid": "0",
            //    "conn": "Server=cnps-mis-yfw;User Id=sa;Password=123;Database=northwind1;"
            //  },
            //  {
            //    "dbid": "1",
            //    "conn": "Server=cnps-mis-yfw;User Id=sa;Password=456;Database=northwind2;"
            //  },
            //  {
            //    "dbid": "2",
            //    "conn": "Server=cnps-mis-yfw;User Id=sa;Password=789;Database=northwind3;"
            //  }
            //]
            //settings结果
            //{
            //  "name": "test123",
            //  "isValue": false,
            //  "counter": 123
            //}
        }
        public class dbconfig
        {
            public string dbid { get; set; }
            public string conn { get; set; }
        }
        public class Settings
        {
            public string Name { get; set; }
            public bool IsValue { get; set; }
            public int Counter { get; set; }
        }
    }
}

(5)结果