LINQ Inner Join

17 Mar 2025 | 阅读 2 分钟

在 LINQ 中，内连接用于仅从集合中返回基于指定条件的匹配记录或元素。

LINQ 内连接的语法

这是使用 LINQ 内连接从集合中获取基于指定条件的元素的语法。

var result = from d in objDept
join e in objEmp
on d.DepId equals e.DeptId
select new
{
EmployeeName = e.Name,
DepartmentName = d.DepName
};

从上面的语法中，我们尝试从“objEmp”、“objDept”集合中获取基于匹配“DeptId”列值的元素。

LINQ 内连接的示例

这是使用 LINQ Inner 连接从集合中获取基于指定条件的元素的示例。

C# 代码

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Programme2
    {
        static void Main(string[] args)
        {
   /* create an object of the class 'department' and create a 
    list of the department with the added record*/
            List<Department> Dept = new List<Department>
    (){
    new Department{DepId=1,DepName="Software"},
    new Department{DepId=2,DepName="Finance"},
    new Department{DepId=3,DepName="Health"}
    };
    /* create an object of the class 'Employee' and create a
    list of the Employee with the added record*/
    List<Employee>Emp = new List<Employee>
    ()
    {
    new Employee { EmpId=1,Name = "Akshay Tyagi", DeptId=1 },
    new Employee { EmpId=2,Name = "Vaishali Tyagi", DeptId=1 },
    new Employee { EmpId=3,Name = "Arpita Rai", DeptId=2 },
    new Employee { EmpId=4,Name = "Sateesh Alavala", DeptId =2},
    new Employee { EmpId=5,Name = "Madhav Sai"}
    };
    /*Linq query apply to fetch the information of the
    employee name and department name
    here we mapped the employee with the department and store the result in the variable 'result'*/
    var result = from d in Dept
    join e in Emp
    on d.DepId equals e.DeptId
    select new
    {
    EmployeeName = e.Name,
    DepartmentName = d.DepName
    };
    //foreach loop traverse all the data in the result variable and store in item variable
    foreach (var item in result)
    {
   /* Console.WriteLine(item.EmployeeName + "\t | " + item.DepartmentName)
    will print the name of the employee and name of the department*/
    Console.WriteLine(item.EmployeeName + "\t | " + item.DepartmentName);
    }
    Console.ReadLine();
    }
    }
    //Create class 'Department' and 'Employee' and set the variable name
    class Department
    {
    public int DepId { get; set; }
    public string DepName { get; set; }
    }
    class Employee
    {
    public int EmpId { get; set; }
    public string Name { get; set; }
    public int DeptId { get; set; }
    }
    }

输出