c# - 你什么时候想在 C# 中嵌套类？

Question

<分区>

Answer 1

当嵌套类仅由外部类使用时，一个很好的例子(不再需要)是集合的枚举器类。

另一个示例可能是用枚举替换类中方法使用的真假参数，以阐明调用签名...

代替

public class Product
{
    public void AmountInInventory(int warehouseId, bool includeReturns)
    {
        int totalCount = CountOfNewItems();
        if (includeReturns)
            totalCount+= CountOfReturnedItems();
        return totalCount;
    }
}

和

  product P = new Product();
  int TotalInventory = P.AmountInInventory(123, true);  

这使得“true”的含义不清楚，您可以这样写:

public class Product
{
    [Flags]public enum Include{None=0, New=1, Returns=2, All=3 }
    public void AmountInInventory(int warehouseId, Include include)
    {
        int totalCount = 0;
        if ((include & Include.New) == Include.New)
            totalCount += CountOfNewItems();
        if ((include & Include.Returns) == Include.Returns)
            totalCount += CountOfReturns();
        return totalCount;
    }
}


  product P = new Product();
  int TotalInventory = P.AmountInInventory(123, Product.Include.All);  

这使得参数值在客户端代码中清晰可见。