ASP.NET Core 入门教程1 ASP.NET Core 读取配置文件

ASP.NET Core 对于读取配置文件，和之前.NET Framework 有了很大的区别，下面将介绍一下在学习ASP.NET Core过程中的配置文件的读取操作。

点击下载源代码。

1、用VS2019新建一个ASP.NET Core Web 应用程序，MVC项目，如下图：

　　

　　

　　

2、 “key:"value" 格式读取 读取配置文件

/*
* 按照关键字直接读取 2种方法 0级目录 型如 “key:"value" 格式
* "TestReadConfig": "这是从配置文件读取的关键字为【TestReadConfig】的内容。",
*/
var testReadConfig1 = Configuration.GetValue(typeof(string), "TestReadConfig");
//或者这种写法也可以
testReadConfig1 = Configuration.GetValue<string>("TestReadConfig");

//第二种写法
var testReadConfig2 = Configuration.GetSection("TestReadConfig").Value;

3、"Key": {"key": "value" } ==>"ConnectionStrings": {"Default": "Server=;" } 2种方法读取

/*
* 按照关键字直接读取 2种方法 1级目录
* "ConnectionStrings": {"Default": "Server=;" }
*/

/*
* 按照关键字直接读取 2种方法 1级目录
* "ConnectionStrings": {"Default": "Server=;" }
*/

var connectionStrings1 = Configuration.GetSection("ConnectionStrings").GetChildren().FirstOrDefault()?.Value;//默认取第一个
var connectionStrings2 = Configuration.GetSection("ConnectionStrings:Default").Value;//键值对取值

/*
键值对读取方法
"Student": {
"Name": "小明",
"Age": 18
}
*/
var keyValueName = Configuration.GetSection("Student:Name").Value;
var keyValueAge = Configuration.GetSection("Student:Age").Value;

4、组合实体类

/*
* 组合实体类
* "Student": {
"Name": "小明",
"Age": 18
}
*/

int age = -99;
var student = Configuration.GetSection("Student").GetChildren()
.Select(config => new Student()
{
Name = config["Name"],
Age = int.TryParse(config["Age"], out age) == true ? age : age,
});

代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Runtime;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

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

　　　　　　　　//加载配置文件方法1
            /*var builder = new ConfigurationBuilder().AddJsonFile("AppSettings.json");
            Configuration = builder.Build();*/

            //加载配置文件方法2
            /*Configuration = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("AppSettings.json").Build();*/

        }

        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.AddControllersWithViews();
        }

        // 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();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

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

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
            /*
            {
              "Logging": {
                "LogLevel": {
                  "Default": "Information",
                  "Microsoft": "Warning",
                  "Microsoft.Hosting.Lifetime": "Information"
                }
              },
              "AllowedHosts": "*",

              "ConnectionStrings": {
                "Default": "Server=;"
              },
              "TestReadConfig": "这是从配置文件读取的关键字为【TestReadConfig】的内容。",
              "Student": {
                "Name": "小明",
                "Age": 18
              }
            }
             */
            /*
             * 按照关键字直接读取 2种方法 0级目录 型如 “key:"value" 格式
             * "TestReadConfig": "这是从配置文件读取的关键字为【TestReadConfig】的内容。",
             */
            var testReadConfig1 = Configuration.GetValue(typeof(string), "TestReadConfig");
            //或者这种写法也可以
            testReadConfig1 = Configuration.GetValue<string>("TestReadConfig");

            //第二种写法
            var testReadConfig2 = Configuration.GetSection("TestReadConfig").Value;

            /*
            * 按照关键字直接读取 2种方法 1级目录
            *  "ConnectionStrings": {"Default": "Server=;" }
            */
            var connectionStrings1 = Configuration.GetSection("ConnectionStrings").GetChildren().FirstOrDefault()?.Value;//默认取第一个
            var connectionStrings2 = Configuration.GetSection("ConnectionStrings:Default").Value;//键值对取值


            /*
             键值对读取方法
              "Student": {
                        "Name": "小明",
                        "Age": 18
                      }
             */
            var keyValueName = Configuration.GetSection("Student:Name").Value;
            var keyValueAge = Configuration.GetSection("Student:Age").Value;

            /*
             * 组合实体类
             *   "Student": {
                        "Name": "小明",
                        "Age": 18
                      }
             */

            int age = -99;
            var student = Configuration.GetSection("Student").GetChildren()
                .Select(config => new Student()
                {
                    Name = config["Name"],
                    Age = int.TryParse(config["Age"], out age) == true ? age : age,
                });

            #region MyRegion
            /*var studentIConfigurationSectionList = Configuration.GetSection("Student").GetChildren().ToList<IConfigurationSection>();
           if (studentIConfigurationSectionList !=null && studentIConfigurationSectionList.Count>0)
           {
               foreach (var item in studentIConfigurationSectionList)
               {

               }
           }*/
            #endregion
        }

        private class Student
        {
            public string? Name { get; set; }
            public int? Age { get; set; }
        }
    }
}

appsettings.json配置文件如下：

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },

  //方法1 Configuration.GetValue(typeof(string), "TestReadConfig"); 或者 Configuration.GetValue<string>("TestReadConfig");
  //方法2  Configuration.GetSection("TestReadConfig").Value;
  "AllowedHosts": "*",
  "TestReadConfig": "这是从配置文件读取的关键字为【TestReadConfig】的内容。",

  //方法1 Configuration.GetSection("ConnectionStrings").GetChildren().FirstOrDefault()?.Value;//默认取第一个
  //方法2 Configuration.GetSection("ConnectionStrings:Default").Value; //键值对取值
  "ConnectionStrings": {
    "Default": "Server=;"
  },

  //组合实体类
  // int age = -99;
  // var student = Configuration.GetSection("Student").GetChildren()
  // .Select(config => new Student()
  // {
  //Name = config["Name"],
  // Age = int.TryParse(config["Age"], out age) == true ? age : age,
  //});
  "Student": {
    "Name": "小明",
    "Age": 18
  }
}

代码截图如下(图片可能有点小，需要放大来看)：

附上源代码，一起学习

下载地址：

https://files-cdn.cnblogs.com/files/ningxt/ASP.NETCore%E5%85%A5%E9%97%A81%E8%AF%BB%E5%8F%96%E9%85%8D%E7%BD%AE%E6%96%87%E4%BB%B6_20191225_Ning.ASP.NETCore3.Study.7z