Question

Employee表包含Departmentid个外键，与Department表的Id列有关。

现在，如果我从Employee表中选择所有行，我应该在DepartmentId表的外键列中获取各自Employee的部门名称。

我正在使用实体框架我可以通过创建Department表的另一个对象来使用连接做事。

输出应该是：

EmployeeName    EmployeeAddress  EmployeeDepartment
    abc            xyz                  IT

它应该自动获取Employee

的外键值

lamiEntities1 lam = new lamiEntities1();
        var query =( from sls in lam.sales.AsEnumerable() join it in lam.items on sls.ItemId equals it.Id orderby sls.Id descending
                    select new

                    {
                        ItemName = it.ItemName,
                        TotalAmounts = sls.Amount,
                        Remarks=sls.Remarks,
                        Dates = sls.Date

                    }).Take(20);

        GridView1.DataSource = query;
        GridView1.DataBind();

这里我如何删除连接并使用itemid forign key

直接使用itemname

Answer 1

我想这就是你要找的东西：

您可以制作DTO（数据传输对象），在层之间传输数据

public class EmployeeWithDepartmentDto
{
    public string EmployeeName { get; set; }
    public string EmployeeAddress { get; set; }
    public string DepartmentName { get; set; }
}

你得到的结果如下：

var result = employeeRepository.Select(e => new EmployeeWithDepartmentDto { EmployeeName = e.Name, EmployeeAddress = e.Address, DepartmentName = e.Department.Name });

foreach (var employeeWithDepartmentDto in result)
     Console.WriteLine($"Name: {employeeWithDepartmentDto.EmployeeName}, Address: {employeeWithDepartmentDto.EmployeeAddress}, Department: {employeeWithDepartmentDto.DepartmentName}");

Here is an example in DotNetFiddle

如果您不想创建DTO类，可以使用匿名对象进行查询

var result = employeeRepository.Select(e => new { EmployeeName = e.Name, EmployeeAddress = e.Address, DepartmentName = e.Department.Name });

或者您可以使用Linq-To-Sql进行查询：

var result = from e in employeeRepository
                select new EmployeeWithDepartmentDto
                {
                    EmployeeName = e.Name,
                    EmployeeAddress = e.Address,
                    DepartmentName = e.Department.Name
                }

如果您使用EF Eager Loading，则必须使用Include：

lamiEntities1 lam = new lamiEntities1();
    var query =( from sls in lam.sales.Include("item")
                orderby sls.Id descending
                select new

                {
                    ItemName = sls.Item.ItemName,
                    TotalAmounts = sls.Amount,
                    Remarks=sls.Remarks,
                    Dates = sls.Date

                }).Take(20);

在没有加入的情况下获取外键值In Entity-to-Linq

1 个答案: