LINQ |分区操作员| TakeWhile
原文:https://www . geeksforgeeks . org/linq-partition-operator-take while/
在 LINQ，分区运算符用于将给定的序列分成两部分，而无需对元素进行排序，并返回其中一部分。标准查询运算符支持 4 种不同类型的分区运算符:
- 跳过
- 滑行同时
- 取
- 趁
TakeWhile 运算符
TakeWhile 运算符用于从给定的序列中返回元素，只要它满足给定的条件，并且当条件满足时，它跳过那些不满足给定条件的元素。该方法以两种不同的方式过载:
- take while(IEnumerable，Func < TSource，Boolean > ): 只要指定条件为真，此方法就用于从给定序列返回元素。
- take while(IEnumerable，Func < TSource，Int32，Boolean > ): 只要指定条件为真，此方法用于从给定序列返回元素。元素的索引值用于谓词函数的逻辑中。
要点:
- 它不支持 C# 和 VB.Net 语言中的查询语法。但是您可以使用 TakeWhile 方法来查询变量，或者您可以将查询包装在括号中，然后调用 TakeWhile 方法。
- 它支持 C# 和 VB.Net 语言中方法语法。
- 它同时出现在可查询类和可枚举类中。
- 它通过使用延迟执行来实现。
- 如果源或条件为空，它将引发 ArgumentNullException。
例 1:
// C# program to illustrate the
// concept of TakeWhile operator
using System;
using System.Linq;
class GFG {
static public void Main()
{
// Data source
int[] sequence = {45, 67, 89, 13, 56,
76, 100, 90};
// Query to pick those elements
// which are less than 70
// Using TakeWhile method
var result = sequence.OrderBy(s => s).TakeWhile(s => s < 70);
Console.WriteLine("New Sequence: ");
// Display new sequence
foreach(var val in result)
{
Console.WriteLine(val);
}
}
}
Output:
New Sequence:
13
45
56
67
例 2:
// C# program to get the names of the
// employees whose salary is less
// than 50000
using System;
using System.Linq;
using System.Collections.Generic;
// Employee details
public class Employee {
public int emp_id
{
get;
set;
}
public string emp_name
{
get;
set;
}
public string emp_gender
{
get;
set;
}
public string emp_hire_date
{
get;
set;
}
public int emp_salary
{
get;
set;
}
}
public class GFG {
// Main method
static public void Main()
{
List<Employee> emp = new List<Employee>() {
new Employee() {emp_id = 209, emp_name = "Anjita", emp_gender = "Female",
emp_hire_date = "12/3/2017", emp_salary = 20000},
new Employee() {emp_id = 210, emp_name = "Soniya", emp_gender = "Female",
emp_hire_date = "22/4/2018", emp_salary = 30000},
new Employee() {emp_id = 211, emp_name = "Rohit", emp_gender = "Male",
emp_hire_date = "3/5/2016", emp_salary = 40000},
new Employee() {emp_id = 212, emp_name = "Anu", emp_gender = "Female",
emp_hire_date = "4/8/2017", emp_salary = 80000},
new Employee() {emp_id = 213, emp_name = "Anil", emp_gender = "Male",
emp_hire_date = "12/1/2016", emp_salary = 60000},
new Employee() {emp_id = 214, emp_name = "Anju", emp_gender = "Female",
emp_hire_date = "17/6/2015", emp_salary = 50000},
};
// Query to get the names of the
// employees whose salary is less
// than 50000 Using TakeWhile method
var res = emp.TakeWhile(e => e.emp_salary < 50000);
foreach(var val in res)
{
Console.WriteLine("Employee Name: {0}",
val.emp_name);
}
}
}
Output:
Employee Name: Anjita
Employee Name: Soniya
Employee Name: Rohit
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