Linq

//Linq:language Intergarted Query 语言整合查询
            //select * from tb_name
            //条件必须实现IEnumerable接口
            //Linq to SQL,Linq to Xml ,Linq to DataSet,Linq to Objects
            int[] numbers = { 5, 10, 8, 3, 6, 12 };
            //Query Systax
            var numQuery1 = from num in numbers
                            where num % 2 == 0
                            orderby num
                            select num;
            foreach (int num in numQuery1)
            {
                Console.WriteLine(num);
            }
            //method Systax
            var numQuery2 = numbers.Where(n => n % 2 == 0).OrderBy(n => n);
            foreach (int num in numQuery2)
            {
                Console.WriteLine(num);
            }
            Console.ReadLine();

语法

        private static void QuerySysnax()
        {
            //1.datasource
            double[] numbers = { 110.00, 1, 2, 3, 4, 5, 6, 7 };
            //2.query creation
            var numquery = from num in numbers
                           where num % 2 == 0
                           select num;
            int numCount = numquery.Count();
            //3.query execution
            Console.WriteLine("1234567890");
            foreach (double num in numquery)
            {
                Console.WriteLine("{0,10}", num);
            }
        }

基本操作

from 获取数据源

where 过滤条件

order 排序

select 获取结果

group 

group into打包(group 一起用)

join 

let 中间变量

private static void myquery()
        {
            string[] mystrings = { "Hello qxw.", "This is Friday!", "Are you Happy?" };
            var stringQuery = from s in mystrings
                              let words = s.Split(' ')
                              from word in words
                              let w = word.ToUpper()
                              select w;
            //var stringQuery = from s in mystrings
            //                  let w = s.ToUpper()
            //                  select w;
            foreach (var s in stringQuery)
            {
                Console.Write("{0} ", s);
            }
        }