.NET Core在类库中读取配置文件appsettings.json

直接上代码，appsettings.json文件内容如下：

{
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "ConnectionStrings": {
    "CxyOrder": "Server=LAPTOP-AQUL6MDE\\MSSQLSERVERS;Database=CxyOrder;User ID=sa;Password=123456;Trusted_Connection=False;"
  },
  "Appsettings": {
    "SystemName": "PDF .NET CORE",
    "Date": "2017-07-23",
    "Author": "PDF"
  },
  "ServiceUrl": "https://www.baidu.com/getnews"
}

建一个项目名称为Common的类库项目，并给该类库项目引入 Microsoft.Extensions.Configuration 和 Microsoft.Extensions.Configuration.Json程序包，类库中加载appsettings.json配置文件代码如下：

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Configuration.Json;

namespace Common
{
    /// <summary>
    /// 读取配置文件
    /// </summary>
    public class AppConfigurtaionServices
    {
        public static IConfiguration Configuration { get; set; }
        static AppConfigurtaionServices()
        {
            //ReloadOnChange = true 当appsettings.json被修改时重新加载            
            Configuration = new ConfigurationBuilder()
            　　.Add(new JsonConfigurationSource { Path = "appsettings.json", ReloadOnChange = true })
            　　.Build();            
        }
    }
}

读取配置文件的代码完成了，只要引用了NetCoreOrder.Common类库的项目中都能方便读取数据库链接字符串和其他配置，使用方法如下：

AppConfigurtaionServices.Configuration.GetConnectionString("CxyOrder"); 
//得到 Server=LAPTOP-AQUL6MDE\\MSSQLSERVERS;Database=CxyOrder;User ID=sa;Password=123456;Trusted_Connection=False;

读取一级配置节点配置

AppConfigurtaionServices.Configuration["ServiceUrl"];
//得到 https://www.baidu.com/getnews

读取二级子节点配置

AppConfigurtaionServices.Configuration["Appsettings:SystemName"];
//得到 PDF .NET CORE
AppConfigurtaionServices.Configuration["Appsettings:Author"];
//得到 PDF

注意，如果AppConfigurtaionServices类中抛出FileNotFoundException异常，说明目录下未找到appsettings.json文件，这时请在项目appsettings.json文件上右键——属性——将“复制到输出目录”项的值改为“始终复制”即可。