Linq的基本语法概述
这篇文章主要介绍“Linq的基本语法概述”,在日常操作中,相信很多人在Linq的基本语法概述问题上存在疑惑,小编查阅了各式资料,整理出简单好用的操作方法,希望对大家解答”Linq的基本语法概述”的疑惑有所帮助!接下来,请跟着小编一起来学习吧!
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在向大家详细介绍Linq基本语法之前,首先让大家了解下调用Enumberalbe扩展函数,然后全面介绍Linq基本语法。
Linq基本语法
var result = from item in container orderby value ascending/descending select item;
1、获取全部记录
var allCars = from c in myCars select c;
2、只获取字段名称
var names = from c in myCars select c.PetName;
这里names就是隐式类型的变量。
3、使用Enumerable.Distinct
var makes = (from c in myCars select c.Make).Distinct();
4、即可以在定义的时候调用Enumberalbe扩展函数
var names = from c in myCars select c.PetName; foreach (var n in names) { Console.WriteLine("Name: {0}", n); }
也可以在兼容的数组类型上调用
var makes = from c in myCars select c.Make; Console.WriteLine("Distinct makes:"); foreach (var m in makes.Distinct()) { Console.WriteLine("Make: {0}", m); }
// Now get only the BMWs. var onlyBMWs = from c in myCars where c.Make == "BMW" select c;
// Get BMWs going at least 100 mph. var onlyFastBMWs = from c in myCars where c.Make == "BMW" && c.Speed >= 100 select c;
5、生成新的数据类型(投影)
var makesColors = from c in myCars select new {c.Make, c.Color};
6、Reverse
或者
var subset = (from c in myCars select c).Reverse(); foreach (Car c in subset) { Console.WriteLine("{0} is going {1} MPH", c.PetName, c.Speed); }
7、排序
默认是ascending
// Order all the cars by PetName. var subset = from c in myCars orderby c.PetName select c; // Now find the cars that are going less than 55 mph, // and order by descending PetName subset = from c in myCars where c.Speed > 55 orderby c.PetName descending select c;
默认顺序时也可以明确指明
var subset = from c in myCars orderby c.PetName ascending select c;
8、Enumerable.Except()
两个IEnumerable
static void GetDiff() { ListmyCars = new List { "Yugo", "Aztec", "BMW"}; List yourCars = new List { "BMW", "Saab", "Aztec" }; var carDiff =(from c in myCars select c) .Except(from c2 in yourCars select c2); Console.WriteLine("Here is what you don't have, but I do:"); foreach (string s in carDiff) Console.WriteLine(s); // Prints Yugo. }
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