1.查詢語(yǔ)法?

Query Syntax:

from <range variable> in <IEnumerable<T> or IQueryable<T> Collection><Standard Query Operators> <lambda expression><select or groupBy operator> <result formation>

?

　　

// string collection IList<string> stringList = new List<string>() { "C# Tutorials","VB.NET Tutorials","Learn C++","MVC Tutorials" ,"Java" };// LINQ Query Syntax var result = from s in stringListwhere s.Contains("Tutorials") select s;

查詢語(yǔ)法以From開(kāi)頭，后面緊跟著Range veriable變量，From從句像這樣的結(jié)構(gòu)"From?rangeVariableName?in?IEnumerablecollection"，意思是從集合的每個(gè)對(duì)象中獲取，它有點(diǎn)像foreach循環(huán)，

?foreach(Student s in studentList)

在From從句之后，我們可以使用不同的標(biāo)準(zhǔn)查詢運(yùn)算符來(lái)過(guò)濾、分類和聯(lián)合集合里面的元素，大概有50個(gè)標(biāo)準(zhǔn)查詢操作

一般以Select 或Group從句結(jié)尾，Select從句用來(lái)構(gòu)建數(shù)據(jù)，你可以查詢?nèi)繉?duì)象或者它的幾個(gè)屬性。

?

IList<Student> studentList = new List<Student>>() { new Student() { StudentID = 1, StudentName = "John", Age = 13} ,new Student() { StudentID = 2, StudentName = "Moin", Age = 21 } ,new Student() { StudentID = 3, StudentName = "Bill", Age = 18 } ,new Student() { StudentID = 4, StudentName = "Ram" , Age = 20} ,new Student() { StudentID = 5, StudentName = "Ron" , Age = 15 } };// LINQ Query Syntax to find out teenager students var teenAgerStudent = from s in studentListwhere s.Age > 12 && s.Age < 20select s;

?

?

LINQ Method Syntax

// string collection IList<string> stringList = new List<string>() { "C# Tutorials","VB.NET Tutorials","Learn C++","MVC Tutorials" ,"Java" };// LINQ Query Syntax var result = stringList.Where(s => s.Contains("Tutorials"));

?

?

?

// Student collection IList<Student> studentList = new List<Student>() { new Student() { StudentID = 1, StudentName = "John", Age = 13} ,new Student() { StudentID = 2, StudentName = "Moin", Age = 21 } ,new Student() { StudentID = 3, StudentName = "Bill", Age = 18 } ,new Student() { StudentID = 4, StudentName = "Ram" , Age = 20} ,new Student() { StudentID = 5, StudentName = "Ron" , Age = 15 } };// LINQ Method Syntax to find out teenager students var teenAgerStudents = studentList.Where(s => s.Age > 12 && s.Age < 20).ToList<Student>();

?

?

?

Standard Query Operators:

Standard Query Operators in Query Syntax:

?

Standard Query Operators in Method Syntax:

?

標(biāo)準(zhǔn)查詢操作根據(jù)功能分類?

ClassificationStandard Query Operators

Filtering（篩選）	Where, OfType
Sorting（排序）	OrderBy, OrderByDescending, ThenBy, ThenByDescending, Reverse
Grouping（分組）	GroupBy, ToLookup
Join（連接）	GroupJoin, Join
Projection（投影）	Select, SelectMany
Aggregation（聚集）	Aggregate, Average, Count, LongCount, Max, Min, Sum
Quantifiers（量詞）	All, Any, Contains
Elements（元素）	ElementAt, ElementAtOrDefault, First, FirstOrDefault, Last, LastOrDefault, Single, SingleOrDefault
Set（集合）	Distinct, Except, Intersect, Union
Partitioning（分割）	Skip, SkipWhile, Take, TakeWhile
Concatenation（連接）	Concat
Equality	SequenceEqual
Generation	DefaultEmpty, Empty, Range, Repeat
Conversion	AsEnumerable, AsQueryable, Cast, ToArray, ToDictionary, ToList

?

轉(zhuǎn)載于:https://www.cnblogs.com/lanpingwang/p/6602024.html

總結(jié)

以上是生活随笔為你收集整理的LINQ 学习路程 -- 查询语法 LINQ Query Syntax的全部?jī)?nèi)容，希望文章能夠幫你解決所遇到的問(wèn)題。

如果覺(jué)得生活随笔網(wǎng)站內(nèi)容還不錯(cuò)，歡迎將生活随笔推薦給好友。