LINQ |分区运算符|拿

在LINQ中，分区运算符用于将给定序列分为两部分，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：

1. 跳过
2. 跳过而
3. 拿
4. 边走边走

带算子

Take运算符用于从序列开始处返回指定数量的相邻元素。换句话说，我们可以说它从第一个项目开始返回指定数量的项目。如下例所示：

重要事项：

• 它不支持C＃和VB.Net语言的查询语法。但是您可以使用Take方法查询变量，也可以将查询括在方括号中，然后调用Take方法。如示例2所示。
• 它支持C＃和VB.Net语言的方法语法。
• 它同时存在于Queryable和Enumerable类中。
• 它是通过使用延迟执行来实现的。
• 如果源为null，它将抛出ArgumentNullException。

范例1：

// C# program to illustrate the
// concept of Taking operator
using System;
using System.Linq;
  
class GFG {
  
    // Main Method
    static public void Main()
    {
  
        // Data source
        int[] sequence = {45, 67, 89,
                     13, 56, 76, 67};
  
        // Query which picks starting 5 ordered
        // elements from the given sequence
        // Using Take method
        var result = sequence.OrderBy(s => s).Take(5);
  
        Console.WriteLine("New Sequence: ");
  
        // Display new sequence
        foreach(var val in result)
        {
            Console.WriteLine(val);
        }
    }
}

输出：

New Sequence: 
13
45
56
67
67

范例2：

// C# program to find the names
// of the first 4 employees
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 emp = new List() {
  
            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 find the names 
        // of the first 4 employees
        // Using Take method
        var res = (from e in emp
                   select e.emp_name)
                   .Take(4);
  
        foreach(var val in res)
        {
            Console.WriteLine("Employee Name: {0}", val);
        }
    }
}

输出：

Employee Name: Anjita
Employee Name: Soniya
Employee Name: Rohit
Employee Name: Anu