Question

我有以下业务对象：

    public class ItemCategoryBO
    {
       public string ItemCategory { get; set; }
       public string Title { get; set; }
    }

    public class ItemBO
    {
       public int ItemId { get; set; }
       public string Title { get; set; }
       public string ItemCategory { get; set; } 
    }

    List<ItemCategoryBO> categoryList = new List<ItemCategoryBO>();

    ItemCategoryBO itemCategory = new ItemCategoryBO();
    itemCategory.ItemCategoryCd = "CARS";
    itemCategory.Title = "Cars";

    ItemCategoryBO itemCategory2 = new ItemCategoryBO();
    itemCategory.ItemCategoryCd = "PLANES";
    itemCategory.Title = "Planes";

    categoryList.Add(itemCategory);
    categoryList.Add(itemCategory2);

    List<ItemBO> itemList = new List<ItemBO>();

    ItemBO item1 = new ItemBO();
    item1.ItemId = 1;
    item1.Title = "1st item";
    item1.ItemCategoryCd = "OTHER";

    ItemBO item2 = new ItemBO();
    item2.ItemId = 2;
    item2.Title = "2nd Item";
    item2.ItemCategoryCd = "CARS";

    ItemBO item3 = new ItemBO();
    item3.ItemId = 3;
    item3.Title = "3rd Item";
    item3.ItemCategoryCd = "PLANES";

    itemList.Add(item1);
    itemList.Add(item2);
    itemList.Add(item3);

如果我有几个类别的列表，我怎样才能找到包含类别列表中类别的项目列表？（在我的例子中，我想回到第2和第3项）

Answer 1

如果您遇到类似情况：

List<ItemBO> items;
List<ItemCategoryBO> categories;

并且您希望获得具有类别列表中所有类别的所有项目，您可以使用此项：

IEnumerable<ItemBO> result = items.Where(item =>
    categories.Any(category => category.ItemCategory.equals(item.ItemCategory)));

Any运算符枚举源序列，如果任何元素满足谓词给出的测试，则返回true。在这种情况下，如果类别列表包含ItemCategoryBO，则其返回true，其ItemCategory字符串与项目的ItemCategory字符串相同。有关MSDN

的更多信息

Answer 2

试试这个：

List<ItemBO> items = ...;
ItemCategoryBO category = ...;

List<ItemBO> filteredItems = items
    .Where( i => i.ItemCategory.Equals(category) )
    .FirstOrDefault();

更新以解决OP的更新问题：

如果我有几个类别的列表，我怎样才能找到包含类别列表中类别的项目列表？（在我的例子中，我想回到第2和第3项）

我认为你实际上应该分两步完成。首先，获取您不同的项目列表。然后，从您的商品中获取您的类别列表。所以：

// First, get the distinct list of items
List<ItemBO> items = new List<ItemBO>();
foreach ( var category in categories )
{
    foreach ( var item in category.Items )
    {
        if ( !items.Contains(item) )
            items.Add(item);
    }
}

// Second, get the list of items that have the category.
List<ItemBO> filteredItems = items
    .Where( i => i.ItemCategory.Equals(category) )
    .FirstOrDefault();

Answer 3

尝试使用一些linq

  List<ItemBO> itm = new List<ItemBO>;
 //Fill itm with data

 //get selected item from control

 string selectedcategory = cboCatetories.SelectedItem;

 var itms = from BO in itm where itm.ItemCategory = selectedcategory                              select itm;

itms now contains all items in that category

Answer 4

这是我在Linqpad

中所做的事情

void Main()
{

    var cat1 = new ItemCategoryBO {ItemCategory="c1", Title = "c1"};
    var cat2 = new ItemCategoryBO {ItemCategory="c2", Title = "c2"};

    var item1 = new ItemBO { ItemId = 1, Title = "item1", ItemCategory="c1"};
    var item2 = new ItemBO { ItemId = 1, Title = "item2", ItemCategory="c2"};
    var item3 = new ItemBO { ItemId = 1, Title = "item3", ItemCategory="c2"};
    var item4 = new ItemBO { ItemId = 1, Title = "item4", ItemCategory="c3"};

    var items = new List() {item1, item2, item3, item4};
    var categories = new List() {cat1, cat2};

    var itemsInCategory = from item in items 
    join category in categories on  item.ItemCategory equals category.ItemCategory into itemInCategory
    from categoryItem in itemInCategory
    select new {item.Title, item.ItemCategory};

    itemsInCategory.Dump(); 
}

// Define other methods and classes here
      public class ItemCategoryBO
        {
           public string ItemCategory { get; set; }
           public string Title { get; set; }
        }

        public class ItemBO
        {
           public int ItemId { get; set; }
           public string Title { get; set; }
           public string ItemCategory { get; set; } 
        }

返回：

Title, ItemCategory
item1 c1 
item2 c2 
item3 c2

Answer 5

希望这会有所帮助：

var result = (Object to search in).Where(m => (Object to compare to).Any(r => r.Equals(m.Key)).ToList();

按另一个列表C＃过滤列表

5 个答案: