标签：sel orm mod res border oid average output clr
在编译代码时，查询语法必须转换未针对.net CLR的方法调用。这些方法调用会调用标准查询运算符(名称未Where、Select、GroupBy、Join、Max和Average等)，也就是表达式查询最终会变成扩展方法查询，只不过表达式查询看起来更明了，更加符合SQL语句的习惯；我习惯使用SQL语句，所以我一般习惯用表达式查询；
from
<range variable>
in
<IEnumerable<T> or IQueryable<T> Collection>
<Standard Query Operators>
<lambda expression>
<select or groupBy operator>
<result formation>
//以from开头,以select结尾;
// 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 stringList
where s.Contains("Tutorials")
select s;
语法： 扩展方法 + Lambda Expression
//例子一
// 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"));
//例子二
// 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>();class QueryVMethodSyntax
{
static void Main()
{
int[] numbers = { 5, 10, 8, 3, 6, 12};
//Query syntax:
IEnumerable<int> numQuery1 =
from num in numbers
where num % 2 == 0
orderby num
select num;
//Method syntax:
IEnumerable<int> numQuery2 = numbers.Where(num => num % 2 == 0).OrderBy(n => n);
foreach (int i in numQuery1)
{
Console.Write(i + " ");
}
Console.WriteLine(System.Environment.NewLine);
foreach (int i in numQuery2)
{
Console.Write(i + " ");
}
// Keep the console open in debug mode.
Console.WriteLine(System.Environment.NewLine);
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
}
/*
Output:
6 8 10 12
6 8 10 12
*/标签：sel orm mod res border oid average output clr
原文地址：https://www.cnblogs.com/maanshancss/p/13137640.html
