NHibernate，表之间连接并返回特定类型答案

【问题标题】：NHibernate, join between tables and return a specific typeNHibernate，表之间连接并返回特定类型
【发布时间】：2012-11-07 20:05:12
【问题描述】：

我有 2 个表，我想在结果类中放置一些字段，但我卡住了。我想要的代码在 Entity Framework 中看起来像这样：

var res =   
(from p in context.EstimationItem
    join q in ...
    select new EstimationWithDetail
    {
        Estimation = q.Estimation,
        Id = q.Id,
        FullName = q.Customer.FirstName + q.Customer.LastName

    }).ToList();

在Nibernate中，此时，我有这个，但我被卡住了......

var res =
    Session.QueryOver<EstimationItem>()
    .JoinQueryOver(x => x.Estimation)
    .Select(
        x => x.Estimation.Reference,
        x => x.Estimation.CreationDate,
        x => x.Price,
        x => x.Estimation.Customer.FirstName,
        x => x.Estimation.Customer.LastName
        )
    .List();

public class Estimation
{
    public virtual string Reference { get; set; }
    public virtual Customer Customer { get; set; }
    public virtual DateTime CreationDate { get; set; }
    public virtual decimal Total { get; set; }
    public virtual IList<EstimationItem> EstimationItems { get; set; }
}

public class EstimationItem
{
    public virtual decimal Price { get; set; }
    public virtual int Quantity { get; set; }
    public virtual Estimation Estimation { get; set; }
    public virtual Product Product { get; set; }
}

public class EstimationWithDetail
{
    public string Reference { get; set; }       //Estimation.Reference
    public string FullName { get; set; }        //concat FirstName and LastName from Customer
    public decimal Price { get; set; }          //Estimation.Total
    public int Id { get; set; }                 //Estimation.Id
    public DateTime CreationDate { get; set; }  //Estimation.CreationDate
}

更新 1

我尝试了代码，但出现此错误： InvalidOperarionException，类型为“EstimationItem”的变量“x”从范围“”中引用，但未定义

var res =
    Session.QueryOver<EstimationItem>()
    .JoinQueryOver(x => x.Estimation)
    .Select(x => new EstimationWithDetail
    {
        Code = x.Estimation.Reference,
        CreationDate = x.Estimation.CreationDate,
        Price = x.Estimation.Total,
        FullName = x.Estimation.Customer.FirstName + x.Estimation.Customer.LastName
    })
    .List<EstimationWithDetail>();

更新 2： 我也试过了

Estimation a = null;
Customer b = null;
var res = Session.QueryOver<EstimationItem>()
    .JoinAlias(c => c.Estimation, () => a)
    .JoinAlias(c => c.Estimation.Customer, () => b)
    .Select(x => new EstimationWithDetail
    {
        Code = a.Reference,
        Id = a.Id,
        FullName = b.LastName
    })
    .List<EstimationWithDetail>();

【问题讨论】：

我也有这个问题。如果我将.Select 移到.List<...>() 之后，它可以工作，但是SQL 选择会选择所有列，这就是我（我们我猜) 试图避免。你找到解决办法了吗？

标签： c# entity-framework nhibernate orm

【解决方案1】：

我对 NHibernate 的 Linq 提供程序不是很熟悉，因为我没有使用过它，但你不能这样做：

var res = Session.QueryOver<EstimationItem>()
    .JoinQueryOver(x => x.Estimation)
    .Select(x => new EstimationWithDetail
    {
        Estimation = x.Estimation,
        Id = x.Id,
        FullName = x.Estimation.Customer.FirstName + x.Estimation.Customer.LastName

    })
    .List();

【讨论】：