c# – 集中或合并LINQ select

如何重构此代码以便我可以集中投影？

public IEnumerable<ItemDto> GetItemsByType(int itemId,ItemType itemType)
{
    IEnumerable<ItemDto> items = null;
    try
    {
        var tempItems= _Items.Get(i => i.ItemId == itemId
            && o.Active == true);
        switch (itemType)
        {
            case ItemType.normal:
                items = from item in tempItems
                        select new ItemDto
                        {
                            // many fields here
                        };
                break;
            case ItemType.damaged:
                items = from item in tempItems
                        join itemDetail in _ItemDetails.Get() on item.ID equals itemDetail.ItemID
                        select new ItemDto
                        {
                            // many fields here
                        };
                break;
            case ItemType.Fixed:
                items = from item in tempItems
                        join itemDetail in _ItemDetails.Get() on item.ID equals itemDetail.ItemID
                        where item.Status.ToLower() == "fixed"
                        select new ItemDto
                        {
                            // many fields here
                        };
                break;

            // more case statements here...

            default:
                break;
        }
    }
    catch { ... }
}

@H_502_4@基本上,我在每个案例陈述中都有很多案例陈述和长期预测.我担心一旦DTO需要改变,比如添加一个新字段,其他情况的投影可能彼此不一致(忘记或错过更新).我该如何集中这个？

解决方法

你能这样接近吗？

var query = tempItems.AsQueryable();

switch(itemType)
{
   case ItemType.damaged:
        query.Join(...);
        break;

   case ItemType.Fixed:
        query.Where(...);
}

query.Select(e => new ItemDto{//Lots of properties});

return query.ToList();