static void Linq1()

 {

     int[] numbers = { , , , , , , , , ,  };

     var first3Numbers = numbers.Take();

     Console.WriteLine("前3个数:");

     foreach (var n in first3Numbers)

     {

         Console.WriteLine(n);

     }

 }

 static void Linq2()

 {

     int[] numbers = { , , , , , , , , ,  };

     var skip3Numbers = numbers.Skip();

     Console.WriteLine("除去前3个数后数字:");

     foreach (var n in skip3Numbers)

     {

         Console.WriteLine(n);

     }

 }

 int currentPageIndex;　　// 当前页号

 int pageSize;　　　　　　// 每页有多少条记录

 source 是总数据源集合

 则用LINQ分页的代码为

 var query = source.Skip((currentPageIndex-) * pageSize).Take(pageSize);

 static void Linq3()

 {

     string[] cates = {"酒类","烟类","肉类" };

     var products = Product.GetDefaultData();

     // CategoryName 没有与 cate 匹配的将被剔除

     var query = from c in cates

                 join p in products on c equals p.CategoryName

                 select new { ShowName = c + " : " + p.ProductName };

     foreach (var item in query)

     {

         Console.WriteLine(item.ShowName);

     }

 }

 public class Product

 {

     public string CategoryName { get; set; }

     public string ProductName { get; set; }

     public static List<Product> GetDefaultData()

     {

         return new List<Product>

         {

             new Product{ CategoryName="烟类", ProductName="中华"},

             new Product{ CategoryName="酒类", ProductName="白酒"},

             new Product{ CategoryName="酒类", ProductName="红酒"},

             new Product{ CategoryName="肉类", ProductName="猪肉"},

             new Product{ CategoryName="肉类", ProductName="牛肉"},

             new Product{ CategoryName="零食", ProductName="饼干"},

             new Product{ ProductName="暂未分类产品1"},

             new Product{ ProductName="暂未分类产品2"},

         };

     }

 }

 static void Linq4()

 {

     string[] cates = { "酒类", "烟类", "肉类" };

     var products = Product.GetDefaultData();

     var query = from c in cates

                 join p in products on c equals p.CategoryName

                 into tgroup

                 select new { Name = c, Group = tgroup };

     foreach (var item in query)

     {

         Console.Write("{0}: ",item.Name);

         foreach (var g in item.Group)

         {

             Console.Write("{0} ",g.ProductName);

         }

         Console.WriteLine();

     }

 }

 static void Linq5()

 {

     string[] cates = { "酒类", "烟类", "肉类" };

     var products = Product.GetDefaultData();

     var query = from c in cates

                 join p in products on c equals p.CategoryName

                 into tgroup

                 from g in tgroup

                 where g.ProductName.Contains("牛腩")  // 仅要产品名字含有牛腩的分组

                 select new { Name = c, Group = tgroup };

     foreach (var item in query)

     {

         Console.Write("{0}: ", item.Name);

         foreach (var g in item.Group)

         {

             Console.Write("{0} ", g.ProductName);

         }

         Console.WriteLine();

     }

 }

 static void Linq6()

 {

     string[] cates = { "酒类", "烟类", "肉类" ,"调料类"};

     var products = Product.GetDefaultData();

     var query = from c in cates

                 join p in products on c equals p.CategoryName

                 into tgroup

                 from g in tgroup.DefaultIfEmpty()

                 select new { Name = c, ProductName = g==null ? "该分组下没有内容":g.ProductName };

     foreach (var item in query)

     {

         Console.WriteLine("{0} {1}",item.Name,item.ProductName);

     }

 }