1.Nuget添加Microsoft.Extensions.Configuration.Json

2.appsettings.json中添加"ConnectionStrings"

{  "Logging": {    "LogLevel": {      "Default": "Warning"    }  },  "ConnectionStrings": {    "SQLConnection": "Data Source=127.0.0.1;Database=xxxx;UID=xx;PWD=xx;",    "OracleConnection": "",    "MySqlConnection": "",    "SqlLiteConnection": ""  },  "AllowedHosts": "*"}

3.新建AppSettingsJson.cs

using Microsoft.Extensions.Configuration;using System.IO;namespace WebAPI{    public class AppSettingsJson    {        public static string ApplicationExeDirectory()        {            var location = System.Reflection.Assembly.GetExecutingAssembly().Location;            var appRoot = Path.GetDirectoryName(location);            return appRoot;        }        public static IConfigurationRoot GetAppSettings()        {            string applicationExeDirectory = ApplicationExeDirectory();            var builder = new ConfigurationBuilder()            .SetBasePath(applicationExeDirectory)            .AddJsonFile("appsettings.json");            return builder.Build();        }    }}

4.C#调用 

var config = AppSettingsJson.GetAppSettings();var sqlconnection = config.GetSection("ConnectionStrings:SQLConnection").Value;var connectionstrings = config.GetSection("ConnectionStrings");var oracleconnection = connectionstrings["OracleConnection"];