Linq将结果联接到List

本文关键字：List 结果 Linq | 更新日期: 2023-09-27 17:57:43

这里有一个linq内部联接，它返回我想要的

 var innerJoinQuery =
                from employee in DbSet
                join department in DbContext.Set<Departments>() on employee.DepartmentID equals department.ID
                select new { ID = employee.ID, FirstName = employee.FirstName, LastName = employee.LastName, DepartmentID = employee.DepartmentID, DepartmentName = department.Name };

            List<Employees> innerjoinresult_as_employees_list = innerJoinQuery.AsEnumerable().Cast<Employees>().ToList();

员工模式为：

public class Employees
    {
        public int ID { get; set; }   
        [Required]
        public string FirstName { get; set; }
        [Required]
        public string LastName { get; set; }
        public int DepartmentID { get; set; }
        [NotMapped]
        public string DepartmentName { get; set; }
    }

我的问题是，我不能将var innerJoinQuery作为List<Employees>，这样我就可以返回它。

有人知道怎么做吗？

Linq将结果联接到List

如果我理解正确，您正在寻找将结果转换为Employees实例列表的方法。

您可以通过更新LINQ语句的投影部分来实现这一点。目前，它投影到一个反义词对象。你想投影到Employees型

var innerjoinresult_as_employees_list =(from employee in DbSet
                                        join department in DbContext.Set<Departments>() 
                                        on employee.DepartmentID equals department.ID
                                        select new Employees { 
                                                   ID = employee.ID, 
                                                   FirstName =  employee.FirstName, 
                                                   LastName = employee.LastName,
                                                   DepartmentID = employee.DepartmentID, 
                                                   DepartmentName = department.Name }
                                        ).ToList();

结果（变量innerjoinresult_as_employees_list的值将是Employees类的列表）

您正在投影到匿名类型，而不是Employee对象。将您的查询更改为：

var innerJoinQuery =
    from employee in DbSet
    join department in DbContext.Set<Departments>()
        on employee.DepartmentID equals department.ID
    select new Employee { ID = employee.ID, 
                          FirstName = employee.FirstName, 
                          LastName = employee.LastName, 
                          DepartmentID = employee.DepartmentID, 
                          DepartmentName = department.Name 
                        };
List<Employees> innerjoinresult_as_employees_list = innerJoinQuery.ToList();

还没有测试过，但请尝试一下；你需要投影到正确的类型：

     var innerJoinQuery =
                (from employee in DbSet
                join department in DbContext.Set<Departments>() on employee.DepartmentID equals department.ID
                select new Employees{ ID = employee.ID, FirstName = employee.FirstName, LastName = employee.LastName, DepartmentID = employee.DepartmentID, DepartmentName = department.Name }).ToList();
List<Employees> employees = new List<Employees>(innerJoinQuery);
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