在.net framework中，配置文件一般采用的是xml格式的，.net framework提供了专门的configurationmanager来读取配置文件的内容，.net core中推荐使用json格式的配置文件，那么在.net core中该如何读取json文件呢？

一、在startup类中读取json配置文件

1、使用configuration直接读取

看下面的代码：

public iconfiguration configuration {
     get;
 }

configuration属性就是.net core中提供的用来读取json文件。例如：

public void configure(iapplicationbuilder app, ihostingenvironment env)
{


            string option1 = $"option1 = {
this.configuration["option1"]}
    ";

            string option2 = $"option2 = {
this.configuration["option2"]}
    ";

            string suboption1 = $"suboption1 = {
this.configuration["subsection:suboption1"]}
    ";

            // 读取数组
            string name1 = $"name={
this.configuration["student:0:name"]}
     ";

            string age1 = $"age= {
this.configuration["student:0:age"]}
    ";

            string name2 = $"name={
this.configuration["student:1:name"]}
    ";

            string age2 = $"age= {
this.configuration["student:1:age"]}
    ";
    
            // 输出
            app.run(c =>
     c.response.writeasync(option1+"\r\n"+option2+ "\r\n"+suboption1+ "\r\n"+name1+ "\r\n"+age1+ "\r\n"+name2+ "\r\n"+age2));

            if (env.isdevelopment())
            {
    
                app.usedeveloperexceptionpage();

            }

            else
            {
    
                app.usehsts();

            }
    

            app.usehttpsredirection();
    
            app.usemvc();

}

结果：

2、使用ioptions接口

1、定义实体类

public class mongodbhostoptions
{

        ////// 连接字符串
        ///public string connection {
     get;
     set;
 }

        ////// 库
        ///public string database {
     get;
     set;
 }


        public string table {
     get;
     set;
 }

}

2、修改json文件

在appsettings.json文件中添加mongodbhost节点：

{

  "logging": {

    "loglevel": {

      "default": "warning"
    }

  }
,
  "option1": "value1_from_json",
  "option2": 2,
  "subsection": {

    "suboption1": "subvalue1_from_json"
  }
,
  "student": [
    {

      "name": "gandalf",
      "age": "1000"
    }
,
    {

      "name": "harry",
      "age": "17"
    }

  ],
  "allowedhosts": "*",
  //mongodb
  "mongodbhost": {

    "connection": "mongodb://127.0.0.1:27017",
    "database": "templatedb",
    "table": "cdatemplateinfo"
  }

}

注意：

mongodbhost里面的属性名必须要和定义的实体类里面的属性名称一致。

3、在startup类里面配置

添加optionconfigure方法绑定

private void optionconfigure(iservicecollection services)
{
    
      //mongodbhost信息
      services.configure(configuration.getsection("mongodbhost"));

}

在configureservices方法中调用上面定义的方法：

public void configureservices(iservicecollection services)
{
    
     // 调用optionconfigure方法
     optionconfigure(services);
               
     services.addmvc().setcompatibilityversion(compatibilityversion.version_2_1);

}
    

在控制器中使用，代码如下：

using system;
    
using system.collections.generic;
    
using system.linq;
    
using system.threading.tasks;
    
using microsoft.aspnetcore.http;
    
using microsoft.aspnetcore.mvc;
    
using microsoft.extensions.options;


namespace readjsondemo.controllers
{

    [route("api/[controller]")]
    [apicontroller]
    public class mongodbcontroller : controllerbase
    {
    
        private readonly mongodbhostoptions _mongodbhostoptions;


        ////// 通过构造函数注入
        //////public mongodbcontroller(ioptionsmongodbhostoptions)
        {
    
            _mongodbhostoptions = mongodbhostoptions.value;

        }


        [httpget]
        public async task get()
        {
    
           await response.writeasync("connection:" + _mongodbhostoptions.connection + "\r\ndatabase;
    " + _mongodbhostoptions.database + "\r\ntable:" + _mongodbhostoptions.table);

        }

    }

}
    

运行结果：

3、读取自定义json文件

在上面的例子中都是读取的系统自带的appsettings.json文件，那么该如何读取我们自己定义的json文件呢？这里可以使用configurationbuilder类。

实例化类

var builder = new configurationbuilder();
    

添加方式1

builder.addjsonfile("path", false, true);

其中path表示json文件的路径，包括路径和文件名。

添加方式2

builder.add(new jsonconfigurationsource {
path= "custom.json",optional=false,reloadonchange=true }
).build()

具体代码如下：

private void customoptionconfigure(iservicecollection services)
{
    
            iconfiguration _configuration;
    
            var builder = new configurationbuilder();
    
            // 方式1
            //_configuration = builder.addjsonfile("custom.json", false, true).build();

            // 方式2
            _configuration = builder.add(new jsonconfigurationsource {
path= "custom.json",optional=false,reloadonchange=true }
    ).build();
    
            services.configure(_configuration.getsection("websiteconfig"));

}

configureservices方法如下：

public void configureservices(iservicecollection services)
{
    
            // 调用optionconfigure方法
            optionconfigure(services);
    
            customoptionconfigure(services);
    
            services.addmvc().setcompatibilityversion(compatibilityversion.version_2_1);

}
    

控制器代码如下：

using system;
    
using system.collections.generic;
    
using system.linq;
    
using system.threading.tasks;
    
using microsoft.aspnetcore.http;
    
using microsoft.aspnetcore.mvc;
    
using microsoft.extensions.options;


namespace readjsondemo.controllers
{

    [route("api/[controller]")]
    [apicontroller]
    public class mongodbcontroller : controllerbase
    {
    
        private readonly mongodbhostoptions _mongodbhostoptions;
    

        private readonly websiteoptions _websiteoptions;


        ////// 通过构造函数注入
        //////public mongodbcontroller(ioptionsmongodbhostoptions,ioptionswebsiteoptions)
        {
    
            _mongodbhostoptions = mongodbhostoptions.value;
    
            _websiteoptions = websiteoptions.value;

        }


        [httpget]
        public async task get()
        {
    
           await response.writeasync("connection:" + _mongodbhostoptions.connection + "\r\ndatabase;
    " + _mongodbhostoptions.database + "\r\ntable:" + _mongodbhostoptions.table);
    
            await response.writeasync("\r\n");
    
            await response.writeasync("websitename:" + _websiteoptions.websitename + "\r\nwebsiteurl;
    " + _websiteoptions.websiteurl);

        }

    }

}
    

二、在类库中读取json文件

在上面的示例中都是直接在应用程序中读取的，那么如何在单独的类库中读取json文件呢？看下面的示例代码：

using microsoft.extensions.configuration;
    
using microsoft.extensions.dependencyinjection;
    
using microsoft.extensions.options;
    
using system;
    
using system.collections.generic;
    
using system.io;
    
using system.text;


namespace common
{

    public class jsonconfighelper
    {

        public static t getappsettings(string filename, string key) where t : class, new()
        {
    
            // 获取bin目录路径
            var directory = appcontext.basedirectory;
    
            directory = directory.replace("\\", "/");


            var filepath = $"{
directory}
/{
filename}
    ";

            if (!file.exists(filepath))
            {
    
                var length = directory.indexof("/bin");

                filepath = $"{
directory.substring(0, length)}
/{
filename}
    ";

            }
    

            iconfiguration configuration;
    
            var builder = new configurationbuilder();
    
            
            builder.addjsonfile(filepath, false, true);
    
            configuration = builder.build();
    

            var appconfig = new servicecollection()
                .addoptions()
                .configure(configuration.getsection(key))
                .buildserviceprovider()
                .getservice()
                .value;
    

            return appconfig;

        }

    }

}

注意：这里要添加如下几个程序集，并且要注意添加的程序集的版本要和.net core web项目里面的程序集版本一致，否则会报版本冲突的错误

• 1、microsoft.extensions.configuration
• 2、microsoft.extensions.configuration.json
• 3、microsoft.extensions.options
• 4、microsoft.extensions.options.configurationextensions
• 5、microsoft.extensions.options

json文件如下：

{

  "websiteconfig": {

    "websitename": "customwebsite",
    "websiteurl": "https:localhost:12345"
  }
,
  "dbconfig": {

    "datasource": "127.0.0.1",
    "initialcatalog": "mydb",
    "userid": "sa",
    "password": "123456"
  }

}
    

dbhostoptions实体类定义如下：

using system;
    
using system.collections.generic;
    
using system.linq;
    
using system.threading.tasks;


namespace readjsondemo
{

    public class dbhostoptions
    {

        public string datasource {
     get;
     set;
 }


        public string initialcatalog {
     get;
     set;
 }


        public string userid {
     get;
     set;
 }


        public string password {
     get;
     set;
 }

    }

}
    

注意：这里的dbhostoptions实体类应该建在单独的类库中，这里为了演示方便直接建在应用程序中了。

在控制器中调用：

using system;
    
using system.collections.generic;
    
using system.linq;
    
using system.threading.tasks;
    
using common;
    
using microsoft.aspnetcore.http;
    
using microsoft.aspnetcore.mvc;
    
using microsoft.extensions.options;


namespace readjsondemo.controllers
{

    [route("api/[controller]")]
    [apicontroller]
    public class mongodbcontroller : controllerbase
    {
    
        private readonly mongodbhostoptions _mongodbhostoptions;
    

        private readonly websiteoptions _websiteoptions;


        ////// 通过构造函数注入
        //////public mongodbcontroller(ioptionsmongodbhostoptions,ioptionswebsiteoptions)
        {
    
            _mongodbhostoptions = mongodbhostoptions.value;
    
            _websiteoptions = websiteoptions.value;

        }


        [httpget]
        public async task get()
        {
    
            dbhostoptions dboptions = jsonconfighelper.getappsettings("custom.json", "dbconfig");
    
            await response.writeasync("datasource:" + dboptions.datasource + "\r\ninitialcatalog;
    " + dboptions.initialcatalog+ "\r\nuserid:"+dboptions.userid+ "\r\npassword"+dboptions.password);
    
            await response.writeasync("\r\n");
    
            await response.writeasync("connection:" + _mongodbhostoptions.connection + "\r\ndatabase;
    " + _mongodbhostoptions.database + "\r\ntable:" + _mongodbhostoptions.table);
    
            await response.writeasync("\r\n");
    
            await response.writeasync("websitename:" + _websiteoptions.websitename + "\r\nwebsiteurl;
    " + _websiteoptions.websiteurl);
           
        }

    }

}
    

运行结果：

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