- linq中的查询数据源包括数组,集合,列表,数据库。
- 简单查询例子:
- public void linqTest()
{
int[] arr = {1,2,3,4,5,6,7,8,9,0 };
var query1 = from val in arr select val;
foreach (var item in query1)
{
Console.WriteLine(item); - }
- }
- 在这个查询中from为查询关键字,val是查询过程中的临时变量,也就是存储每一条查询结果的变量,arr为查询的数据源,select 表示对from查询结果集合的筛选,也就是你想展示给用户看的数据是那些,这里就写相应的变量,比如想展示的是Student类的name属性,就写val.name,想展示age属性就写,val.age
-
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Cshape委托的定义与实现 { class LinqTest { public void linqTest() { int[] arr = {1,2,3,4,5,6,7,8,9,0 }; var query1 = from val in arr select val; foreach (var item in query1) { Console.WriteLine(item); } } static void Main(string [] args) { //new LinqTest().linqTest(); Student[] stuArr = { new Student("张三","男"), new Student("李四","男"), new Student("张三","男"), new Student("小屁孩","女"), new Student("张三","女"), new Student("约翰内僧宝","女"), }; //查询数组中的所有数据 var query = from item in stuArr select item; foreach (var it in query) { Console.WriteLine(it); } var query1 = from item in stuArr select item.Sex; foreach (var ite in query1) { Console.WriteLine(ite); } var quary2 = from item in stuArr select item.Name.Length; foreach (var item in quary2) { Console.Write(item); } var quary3 = from item in stuArr where item.Name == "luoli" select item; foreach (var item in quary3) { Console.Write(item); } var query4 = from item in stuArr where item.Name.Length == 5 && item.Sex == "na" select item; foreach (var item in query4) { Console.Write(item); } var query5 = from item in stuArr orderby item.Sex.Length select item; foreach (var item in query5) { Console.Write(item); } var query6 = from item in stuArr group item by item.Name into arrgre orderby arrgre.Key.Length select arrgre; foreach (var item in query6) { Console.WriteLine(item.Key); foreach (var it in item) { Console.WriteLine(it); } } } } }
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转载自blog.csdn.net/fbw668859/article/details/81004090
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