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法律学如何在 C# 中使用 LINQ 和 Lambda 进行连接？
内联连接仅返回两张表中匹配或已存在的记录或行。我们还可以根据条件在多张表上应用连接，如下所示。如果我们需要根据多条条件执行连接，请使用匿名类型。
在下面的示例中，我们编写了可以在 Linq 中用于执行连接的两种方法，这里将连接部门和员工
示例
class Program{
static void Main(string[] args){
var result =
Employee.GetAllEmployees().Join(Department.GetAllDepartments(),
e => e.DepartmentID,
d => d.ID, (employee, department) => new{
EmployeeName = employee.Name,
DepartmentName = department.Name
});
foreach (var employee in result){
Console.WriteLine(employee.EmployeeName + "\t" +
employee.DepartmentName);
}
var result1 = from e in Employee.GetAllEmployees()
join d in Department.GetAllDepartments()
on e.DepartmentID equals d.ID
select new{
EmployeeName = e.Name,
DepartmentName = d.Name
};
foreach (var employee in result1){
Console.WriteLine(employee.EmployeeName + "\t" +
employee.DepartmentName);
}
Console.ReadLine();
}
}
public class Employee{
public int ID { get; set; }
public string Name { get; set; }
public int DepartmentID { get; set; }
public static List<Employee> GetAllEmployees(){
return new List<Employee>(){
new Employee { ID = 1, Name = "A", DepartmentID = 1 },
new Employee { ID = 2, Name = "B", DepartmentID = 2 },
new Employee { ID = 3, Name = "B", DepartmentID = 1 },
new Employee { ID = 4, Name = "V", DepartmentID = 1 },
new Employee { ID = 5, Name = "F", DepartmentID = 2 },
new Employee { ID = 6, Name = "R", DepartmentID = 2 },
new Employee { ID = 7, Name = "TT", DepartmentID = 1 },
new Employee { ID = 8, Name = "YY", DepartmentID = 1 },
new Employee { ID = 9, Name = "WW", DepartmentID = 2 },
new Employee { ID = 10, Name = "QQ"}
};
}
}
public class Department{
public int ID { get; set; }
public string Name { get; set; }
public static List<Department> GetAllDepartments(){
return new List<Department>(){
new Department { ID = 1, Name = "IT"},
new Department { ID = 2, Name = "HR"},
new Department { ID = 3, Name = "Contract"},
};
}
}输出
A IT B HR B IT V IT F HR R HR TT IT YY IT WW HR A IT B HR B IT V IT F HR R HR TT IT YY IT WW HR
更新于： 2020 年 8 月 19 日
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