聆途笔记

C#配置文件读取：全面解析与应用实践

配置文件是应用程序的重要组成部分，它们使应用程序能够在不重新编译代码的情况下调整行为。在C#中，有多种方法可以读取和处理配置文件，本文将全面介绍这些技术及其最佳实践。

一、配置文件类型概述

1.1 常见配置文件格式对比

格式类型文件扩展名优点缺点适用场景
XML.config, .xml结构清晰，支持复杂配置冗长，可读性一般传统.NET应用，WCF配置
JSON.json轻量，易读，现代标准缺乏注释(标准JSON)ASP.NET Core，Web API
INI.ini简单易读功能有限，无层次结构简单桌面应用
YAML.yaml, .yml人类友好，支持注释缩进敏感，解析复杂Kubernetes，Docker
环境变量–部署友好，安全管理大量变量困难容器化应用，云原生

二、XML配置读取（传统.NET方式）

2.1 App.config/Web.config基础

<!-- App.config示例 -->
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="ApiEndpoint" value="https://api.example.com"/>
    <add key="MaxRetries" value="3"/>
  </appSettings>
  <connectionStrings>
    <add name="DefaultConnection" 
         connectionString="Server=.;Database=MyDB;Integrated Security=true" 
         providerName="System.Data.SqlClient"/>
  </connectionStrings>
</configuration>

2.2 使用ConfigurationManager读取

using System.Configuration;

// 读取appSettings
string apiEndpoint = ConfigurationManager.AppSettings["ApiEndpoint"];
int maxRetries = int.Parse(ConfigurationManager.AppSettings["MaxRetries"]);

// 读取连接字符串
var connectionString = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;

2.3 自定义配置节

<configuration>
  <configSections>
    <section name="customSettings" type="MyApp.CustomConfigurationSection, MyApp"/>
  </configSections>

  <customSettings>
    <servers>
      <add name="Primary" ip="192.168.1.1"/>
      <add name="Secondary" ip="192.168.1.2"/>
    </servers>
  </customSettings>
</configuration>
public class CustomConfigurationSection : ConfigurationSection
{
    [ConfigurationProperty("servers")]
    public ServerCollection Servers => (ServerCollection)base["servers"];
}

public class ServerCollection : ConfigurationElementCollection
{
    protected override ConfigurationElement CreateNewElement() => new ServerElement();

    protected override object GetElementKey(ConfigurationElement element) => ((ServerElement)element).Name;
}

public class ServerElement : ConfigurationElement
{
    [ConfigurationProperty("name", IsKey = true, IsRequired = true)]
    public string Name => (string)base["name"];

    [ConfigurationProperty("ip", IsRequired = true)]
    public string IP => (string)base["ip"];
}

// 使用
var config = (CustomConfigurationSection)ConfigurationManager.GetSection("customSettings");
foreach (ServerElement server in config.Servers)
{
    Console.WriteLine($"{server.Name}: {server.IP}");
}

三、JSON配置读取（现代.NET方式）

3.1 appsettings.json基础

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning"
    }
  },
  "ConnectionStrings": {
    "DefaultConnection": "Server=.;Database=MyDB;Integrated Security=true"
  },
  "AppSettings": {
    "ApiEndpoint": "https://api.example.com",
    "MaxRetries": 3,
    "Timeout": 30.5
  }
}

3.2 ASP.NET Core配置系统

// Program.cs
var builder = WebApplication.CreateBuilder(args);

// 读取配置
string apiEndpoint = builder.Configuration["AppSettings:ApiEndpoint"];
int maxRetries = builder.Configuration.GetValue<int>("AppSettings:MaxRetries");
string connStr = builder.Configuration.GetConnectionString("DefaultConnection");

// 强类型绑定
var appSettings = builder.Configuration.GetSection("AppSettings").Get<AppSettings>();
public class AppSettings
{
    public string ApiEndpoint { get; set; }
    public int MaxRetries { get; set; }
    public double Timeout { get; set; }
}

3.3 控制台应用中使用

using Microsoft.Extensions.Configuration;

var config = new ConfigurationBuilder()
    .SetBasePath(Directory.GetCurrentDirectory())
    .AddJsonFile("appsettings.json")
    .AddJsonFile($"appsettings.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT")}.json", optional: true)
    .AddEnvironmentVariables()
    .Build();

var settings = config.GetSection("AppSettings").Get<AppSettings>();

四、环境变量与多环境配置

4.1 多环境配置文件

appsettings.json
appsettings.Development.json
appsettings.Production.json

4.2 环境变量配置

# Linux/macOS
export AppSettings__ApiEndpoint="https://prod.api.example.com"

# Windows
set AppSettings__ApiEndpoint=https://prod.api.example.com
// 读取环境变量（冒号或双下划线）
var endpoint = builder.Configuration["AppSettings:ApiEndpoint"];

4.3 配置加载优先级

  1. 内存中的KeyPerFile配置
  2. 环境变量
  3. 用户机密(Development环境)
  4. appsettings.{Environment}.json
  5. appsettings.json
  6. 自定义配置提供程序

五、INI文件配置读取

5.1 INI文件示例

[Database]
Server=localhost
Port=5432
Username=admin
Password=secret

[Application]
LogLevel=Debug
MaxConnections=100

5.2 使用Windows API读取

[DllImport("kernel32")]
private static extern int GetPrivateProfileString(
    string section, string key, string def, 
    StringBuilder retVal, int size, string filePath);

public static string ReadIniValue(string filePath, string section, string key)
{
    var sb = new StringBuilder(255);
    GetPrivateProfileString(section, key, "", sb, 255, filePath);
    return sb.ToString();
}

// 使用
string server = ReadIniValue("config.ini", "Database", "Server");

5.3 使用第三方库

dotnet add package IniFileParser
var parser = new IniFileParser.IniFileParser();
IniData data = parser.ReadFile("config.ini");

string username = data["Database"]["Username"];
int maxConn = int.Parse(data["Application"]["MaxConnections"]);

六、YAML配置读取

6.1 YAML示例

database:
  server: "localhost"
  port: 5432
  credentials:
    username: "admin"
    password: "secret"

application:
  log_level: "Debug"
  features:
    - "FeatureA"
    - "FeatureB"

6.2 使用YamlDotNet

dotnet add package YamlDotNet
using YamlDotNet.Serialization;
using YamlDotNet.Serialization.NamingConventions;

var yaml = File.ReadAllText("config.yml");

var deserializer = new DeserializerBuilder()
    .WithNamingConvention(CamelCaseNamingConvention.Instance)
    .Build();

var config = deserializer.Deserialize<AppConfig>(yaml);

public class AppConfig
{
    public DatabaseConfig Database { get; set; }
    public ApplicationConfig Application { get; set; }
}

public class DatabaseConfig
{
    public string Server { get; set; }
    public int Port { get; set; }
    public Credentials Credentials { get; set; }
}

public class Credentials
{
    public string Username { get; set; }
    public string Password { get; set; }
}

七、配置变更监控与热重载

7.1 文件变更监控

var config = new ConfigurationBuilder()
    .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
    .Build();

// 注册变更回调
ChangeToken.OnChange(
    () => config.GetReloadToken(),
    () => Console.WriteLine("配置已更新: " + config["AppSettings:ApiEndpoint"]));

7.2 IOptions模式(ASP.NET Core)

// 注册服务
builder.Services.Configure<AppSettings>(builder.Configuration.GetSection("AppSettings"));

// 控制器中使用
public class MyController : Controller
{
    private readonly AppSettings _settings;

    public MyController(IOptionsMonitor<AppSettings> settings)
    {
        _settings = settings.CurrentValue;
        settings.OnChange(newSettings => 
        {
            _settings = newSettings;
        });
    }
}

八、安全最佳实践

  1. 敏感信息保护：
  • 使用用户机密(Development)：
    bash dotnet user-secrets set "DbPassword" "s3cr3t"
  • 生产环境使用Azure Key Vault或AWS Secrets Manager
  1. 配置文件权限：
  • 限制配置文件访问权限
  • 避免将配置文件提交到版本控制
  1. 连接字符串加密：
   // 使用ProtectedConfigurationProvider
   <connectionStrings configProtectionProvider="DataProtectionConfigurationProvider">
     <EncryptedData>...</EncryptedData>
   </connectionStrings>

九、性能优化技巧

  1. 减少IO操作：
  • 初始化时加载配置，避免重复读取
  • 使用内存缓存配置数据
  1. 延迟加载：
   private Lazy<AppSettings> _settings = new Lazy<AppSettings>(() => 
       LoadConfig<AppSettings>("appsettings.json"));
  1. 选择高效解析器：
  • 对于高性能场景，考虑使用System.Text.Json而非Newtonsoft.Json

十、自定义配置提供程序

10.1 实现IConfigurationProvider

public class MyCustomConfigProvider : ConfigurationProvider, IConfigurationSource
{
    public override void Load()
    {
        // 从自定义源加载数据
        Data["ApiSettings:Endpoint"] = "https://custom.source";
    }

    public IConfigurationProvider Build(IConfigurationBuilder builder)
    {
        return this;
    }
}

// 注册
builder.Configuration.Add(new MyCustomConfigProvider());

10.2 数据库配置提供程序示例

public class DbConfigurationProvider : ConfigurationProvider
{
    private readonly string _connectionString;

    public DbConfigurationProvider(string connectionString)
    {
        _connectionString = connectionString;
    }

    public override void Load()
    {
        using var db = new SqlConnection(_connectionString);
        var settings = db.Query<ConfigEntry>("SELECT Key, Value FROM Settings");

        Data = settings.ToDictionary(
            x => x.Key.Replace(':', ':'), 
            x => x.Value);
    }
}

// 使用
builder.Configuration.Add(new DbConfigurationSource(connectionString));

十一、跨平台注意事项

  1. 路径处理：
   // 使用Path.Combine而非硬编码路径
   var configPath = Path.Combine(AppContext.BaseDirectory, "config", "settings.json");
  1. 大小写敏感：
  • Linux文件系统区分大小写
  • 环境变量命名规范保持一致
  1. 行尾符：
  • 配置文件使用当前系统的行尾符
  • Git可配置自动转换

十二、总结与建议

12.1 技术选型建议

应用类型推荐配置方式
传统.NET框架应用XML配置文件 + ConfigurationManager
ASP.NET Core应用appsettings.json + IConfiguration
控制台应用JSON/INI + 自定义加载
云原生应用环境变量 + Key Vault集成
跨平台桌面应用JSON/YAML + 嵌入式资源

12.2 通用最佳实践

  1. 分层配置：基础配置(文件) + 环境特定配置(环境变量)
  2. 类型安全：使用强类型配置类而非直接访问字符串键
  3. 验证配置：启动时验证必要配置是否存在
  4. 文档化：为配置项添加说明和示例值
  5. 版本控制：配置文件应与代码版本同步

通过合理选择和实现配置读取策略，可以构建出既灵活又健壮的应用程序配置系统，满足从简单桌面应用到复杂云原生系统的各种需求。

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