.NET 面向插件的开发：写一个能“加功能不改代码”的系统

public interface IUserDataImporter
{
    string Name { get; }
    Task<List<User>> ImportAsync();
}

public classExcelUserImporter : IUserDataImporter
{
    publicstring Name => "Excel导入";

    publicasync Task<List<User>> ImportAsync()
    {
        Console.WriteLine("从 Excel 中导入用户...");
        await Task.Delay(500); // 模拟读取
        returnnew List<User> { new User("Excel用户1"), new User("Excel用户2") };
    }
}

public classCsvUserImporter : IUserDataImporter
{
    publicstring Name => "CSV导入";

    publicasync Task<List<User>> ImportAsync()
    {
        Console.WriteLine("从 CSV 中导入用户...");
        await Task.Delay(500);
        returnnew List<User> { new User("CSV用户1") };
    }
}

public classApiUserImporter : IUserDataImporter
{
    publicstring Name => "API导入";

    publicasync Task<List<User>> ImportAsync()
    {
        Console.WriteLine("从外部 API 导入用户...");
        await Task.Delay(500);
        returnnew List<User> { new User("API用户A"), new User("API用户B") };
    }
}

{
  "EnabledImporters": [ "ExcelUserImporter", "ApiUserImporter" ]
}

var config = new ConfigurationBuilder()
    .AddJsonFile("appsettings.json")
    .Build();

var enabled = config.GetSection("EnabledImporters").Get<string[]>();

var importerTypes = Assembly.GetExecutingAssembly()
    .GetTypes()
    .Where(t => typeof(IUserDataImporter).IsAssignableFrom(t) && !t.IsInterface && !t.IsAbstract);

var importers = new List<IUserDataImporter>();

foreach (var type in importerTypes)
{
    if (enabled.Contains(type.Name))
    {
        var instance = (IUserDataImporter)Activator.CreateInstance(type)!;
        importers.Add(instance);
    }
}

foreach (var importer in importers)
{
    Console.WriteLine($"运行插件：{importer.Name}");
    var users = await importer.ImportAsync();
    foreach (var user in users)
        Console.WriteLine($"导入用户：{user.Name}");
}