Question

ASP.NET中的Linq怎么用？

请详细描述，才能得分。谢谢！

Answer 1

一、LINQ查询符列表

Query Operators
Meaning in Life

from, in
Used to define the backbone for any LINQ expression, which allows you to extract a subset of data from a fitting container.

where
Used to define a restriction for which items to extract from a container.

select
Used to select a sequence from the container.

join, on, equals, into
Performs joins based on specified key. Remember, these “joins” do not need to have anything to do with data in a relational database.

orderby, ascending, descending
Allows the resulting subset to be ordered in ascending or descending order.

group, by
Yields a subset with data grouped by a specified value.

另外还有一些没有操作符号，而是以扩展函数（泛型函数）的方式提供的函数：

用不同方式产生结果集： Reverse<>(), ToArray<>(), ToList<>()

集合操作： Distinct<>(), Union<>(), Intersect<>()

统计函数： Count<>(), Sum<>(), Min<>(), Max<>()

二、使用Enumerable获取Counts

为了使用这些Enumerable扩展函数，一般把LINQ查询表达式用括号括起来，先转换为IEnumerable<T>兼容的对象。

static void GetCount()
{
string[] currentVideoGames = {"Morrowind", "BioShock",
"Half Life 2: Episode 1", "The Darkness",
"Daxter", "System Shock 2"};
// Get count from the query.
int numb = (from g in currentVideoGames
where g.Length > 6
orderby g
select g).Count<string>();
// numb is the value 5.
Console.WriteLine("{0} items honor the LINQ query.", numb);
}

Answer 2

一个很简单的LINQ查询例子，查询一个int 数组中小于5的数字，并按照大小顺序排列：
　　class Program
　　{
　　static void Main(string[] args)
　　{
　　int[] arr = new int[] { 8, 5, 89, 3, 56, 4, 1, 58 };
　　var m = from n in arr where n < 5 orderby n select n;
　　foreach (var n in m)
　　{
　　Console.WriteLine(n);
　　}
　　Console.ReadLine();
　　}
　　}

Answer 3

会SQL语句的没人用这东西。这都是微软件给不会写sql人用的。因为会写程序的不一定全会写 sql.