介绍

之前的.Net framework 程序一般使用 App.config 作为配置文件，不过微软在发布跨平台的 .Net core 后开始使用 appsettings.json 作为配置文件，下面就在 .Net 6 控制台应用中创建一个通用类方法来读取 appsettings.json 配置文件。

创建通用读取类

安装包：

Microsoft.Extensions.Configuration
Microsoft.Extensions.Configuration.FileExtensions
Microsoft.Extensions.Configuration.Json

public class ConfigHelper
{
    public static ConfigHelper _Instance;
    private static IConfigurationRoot _ConfigurationRoot;
    private static readonly object _ThisLock = new();

    public ConfigHelper()
    {
        _ConfigurationRoot=new ConfigurationBuilder()
            .SetBasePath(Path.Combine(Directory.GetCurrentDirectory()))
            .AddJsonFile("appsettings.json",optional:false)
            .Build();
    }
    public static ConfigHelper Instance
    {
        get
        {
            lock (_ThisLock)
            {
                _Instance ??= new ConfigHelper();
                return _Instance;
            }
        }
    }

    /// <summary>
    /// Get ConnectionStrings
    /// </summary>
    /// <param name="key"></param>
    /// <param name="defaultValue"></param>
    /// <returns></returns>
    public string? GetConnectionString(string key,string? defaultValue =null)
    {
        string result = _ConfigurationRoot.GetConnectionString(key);
        if(result == null)
            return defaultValue;
        return result;
    }

    /// <summary>
    /// Get appsettings section
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="key"></param>
    /// <param name="defaultValue"></param>
    /// <returns></returns>
    public T GetAppSettings<T>(string key, T defaultValue)
    {
        IConfigurationSection configSection = _ConfigurationRoot.GetSection(key);
        if (configSection.Value != null)
        {
            return (T)Convert.ChangeType(configSection.Value, typeof(T));
        }
        return defaultValue;
    }
}

测试

创建 appsettings.json 文件

{
  "ConnectionStrings": {
    "mongodb": "mongodb://root:pwd@localhost:27017/mydb"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information"
    }
  }
}

1. 读取数据库连接字符串：

   ConfigHelper.Instance.GetConnectionString("mongodb")

2. 读取配置节点

   ConfigHelper.Instance.GetAppSettings("Logging:LogLevel:Default","")

更新于：2022年9月9日

.Net