C#在.NET Core中的配置管理與環(huán)境變量

在.NET Core中，配置管理是通過Microsoft.Extensions.Configuration命名空間提供的

1. 安裝Microsoft.Extensions.Configuration包：

dotnet add package Microsoft.Extensions.Configuration

2. 創(chuàng)建一個appsettings.json文件，用于存儲配置信息：

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=MyDatabase;Trusted_Connection=True;"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*"
}

3. 在Program.cs中設(shè)置配置：

using System;
using System.IO;
using Microsoft.Extensions.Configuration;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var configuration = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .Build();

            var connectionString = configuration.GetConnectionString("DefaultConnection");
            Console.WriteLine($"Connection String: {connectionString}");
        }
    }
}

4. 使用環(huán)境變量。首先，在項目根目錄下創(chuàng)建一個名為appsettings.Development.json的文件，用于存儲開發(fā)環(huán)境的配置信息：

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=MyDevDatabase;Trusted_Connection=True;"
  }
}

接下來，在Program.cs中添加對環(huán)境變量的支持：

using System;
using System.IO;
using Microsoft.Extensions.Configuration;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var environment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Production";

            var configuration = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddJsonFile($"appsettings.{environment}.json", optional: true, reloadOnChange: true)
                .Build();

            var connectionString = configuration.GetConnectionString("DefaultConnection");
            Console.WriteLine($"Connection String: {connectionString}");
        }
    }
}

現(xiàn)在，當(dāng)你運行應(yīng)用程序時，它將根據(jù)ASPNETCORE_ENVIRONMENT環(huán)境變量的值加載相應(yīng)的配置文件。例如，如果你將ASPNETCORE_ENVIRONMENT設(shè)置為"Development"，則應(yīng)用程序?qū)⑹褂胊ppsettings.Development.json中的連接字符串。如果未設(shè)置ASPNETCORE_ENVIRONMENT或其值為"Production"，則應(yīng)用程序?qū)⑹褂胊ppsettings.json中的連接字符串。