高效化退货系统可扩展性设计：业务增长后如何快速适配新需求

// 退货处理服务接口定义
public interface IReturnService
{
    Task ProcessReturnAsync(ReturnRequest request);
    Task CheckReturnStatusAsync(string returnId);
}

// 实现可扩展的退货服务
public class ReturnProcessingService : IReturnService
{
    private readonly IReturnValidationService _validationService;
    private readonly IRefundCalculationService _refundService;
    
    // 依赖注入使服务易于扩展和替换
    public ReturnProcessingService(
        IReturnValidationService validationService,
        IRefundCalculationService refundService)
    {
        _validationService = validationService;
        _refundService = refundService;
    }
    
    public async Task ProcessReturnAsync(ReturnRequest request)
    {
        // 验证退货请求
        var validationResult = await _validationService.ValidateReturnAsync(request);
        if (!validationResult.IsValid)
            return ReturnProcessResult.Failure(validationResult.Errors);
        
        // 计算退款金额
        var refundAmount = await _refundService.CalculateRefundAsync(request);
        
        // 处理退货逻辑
        return ReturnProcessResult.Success(refundAmount);
    }
}

// 定义退货相关领域事件
public class ReturnRequestedEvent
{
    public string ReturnId { get; set; }
    public string OrderId { get; set; }
    public DateTime RequestedAt { get; set; }
    public string Reason { get; set; }
}

// 事件处理器，便于扩展新处理逻辑
public class ReturnEventHandler
{
    private readonly List _subscribers;
    
    public ReturnEventHandler(IEnumerable subscribers)
    {
        _subscribers = subscribers.ToList();
    }
    
    public async Task PublishReturnRequestedAsync(ReturnRequestedEvent @event)
    {
        // 异步通知所有订阅者
        var tasks = _subscribers.Select(s => s.HandleReturnRequestedAsync(@event));
        await Task.WhenAll(tasks);
    }
}

// 新功能只需实现事件订阅接口即可集成
public class NewFeatureSubscriber : IReturnEventSubscriber
{
    public async Task HandleReturnRequestedAsync(ReturnRequestedEvent @event)
    {
        // 处理新业务需求
        await Task.CompletedTask;
    }
}

// 可扩展的退货数据模型
public class ReturnRequest
{
    public int Id { get; set; }
    public string OrderNumber { get; set; }
    public ReturnStatus Status { get; set; }
    public DateTime RequestDate { get; set; }
    
    // 使用JSON字段存储动态属性，便于扩展
    public string ExtendedProperties { get; set; }
    
    // 导航属性用于关联扩展数据
    public virtual ICollection Items { get; set; }
    public virtual ICollection Notes { get; set; }
}

// 通过配置实现灵活的数据映射
public class ReturnConfiguration : IEntityTypeConfiguration
{
    public void Configure(EntityTypeBuilder builder)
    {
        builder.HasKey(r => r.Id);
        builder.Property(r => r.ExtendedProperties)
               .HasConversion(
                   v => JsonSerializer.Serialize(v, null),
                   v => JsonSerializer.Deserialize<>>(v, null));
        
        // 支持软删除以便数据保留和审计
        builder.HasQueryFilter(r => !r.IsDeleted);
    }
}

// 数据库上下文配置
public class ReturnDbContext : DbContext
{
    public DbSet ReturnRequests { get; set; }
    public DbSet ReturnItems { get; set; }
    
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.ApplyConfiguration(new ReturnConfiguration());
        // 应用其他配置...
    }
}