NHibernate查询投影

时间：2018-12-25 09:13:23

标签： c# .net nhibernate fluent-nhibernate queryover

我有两个实体A和B，其中A与B有一对多的关系。我想创建一个NHibernate查询，该查询使用所有A记录来获取所有B实体，其中：

  • A实体处于活动状态
  • 获取的B实体在日期范围内（我有2个c# DateTime对象）。 
entity A
+----+--------+
| id | active |
+----+--------+
|  1 |      1 |
|  2 |      0 |
|  3 |      1 |
+----+--------+

entity B
+----+------+-------+------------+
| id | year | month | foreign_id |
+----+------+-------+------------+
|  1 | 2000 |    11 |          1 |
|  2 | 2001 |    12 |          2 |
|  3 | 2002 |     4 |          1 |
+----+------+-------+------------+

到目前为止，我已经尝试过：

return this.sessionFactory.GetCurrentSession()
    .QueryOver<A>()
    .Where(x => x.Active)
    .JoinQueryOver(x => x.BList)
    .WhereRestrictionOn(y => y.Year * 12 + y.Month) // the problem is here, exception below
    .IsBetween(2000 * 12 + 1) // january 2000
    .And(2010 * 12 + 3) // march 2010
    .List();

System.InvalidOperationException: variable 'x' of type 'Domain.A' referenced from scope '', but it is not defined

通常，我不喜欢以月数为单位计算所有日期的方法（我的应用程序不关心日期，小时数等。）但是，我暂时不希望更改映射（如下所示）。

我希望获得一些帮助来修复这段代码，或者建议我如何做得更好（或最好同时使用）。

更多详细信息：

我的c#实体看起来像这样：

public class A
{
    public virtual int Id { get; set; }
    public virtual int Active { get; set; }
    public virtual IEnumerable<B> BList { get; set; }
}


public class B
{
    public virtual int Month { get; set; }
    public virtual int Year { get; set; }
}


internal class AMapping: ClassMap<A>
{
    public AMapping()
    {
        Table("AObjects");

        Id(x => x.Id, "id");
        Map(x => x.Active, "active");

        HasMany(x => x.BList)
            .Table("Bobjects")
            .KeyColumn("foreign_id")
            .Component(y => {
                  y.Map(b => b.Month, "month");
                  y.Map(b => b.Year, "year");
        });
    }
}

2 个答案:

答案 0 :(得分：0)

我认为这里的一种方法是使用过滤器。首先要做的是通过过滤器类创建过滤器定义，如下所示：

public class MonthsFilter : FilterDefinition
{
    public MonthsFilter()
    {
        WithName("MonthsFilter")
            .AddParameter("startMonths", NHibernateUtil.Int32)
            .AddParameter("endMonths", NHibernateUtil.Int32);
    }
}

然后，您需要通过ClassMap方法将过滤器添加到A的BList中，并添加到ApplyFilter属性中：

internal class AMapping : ClassMap<A>
{
    public AMapping()
    {
        Table("AObjects");

        Id(x => x.Id, "id");
        Map(x => x.Active, "active");

        HasMany(x => x.BList)
            .Table("BObjects")
            .KeyColumn("foreign_id")
            .Component(y => {
                y.Map(b => b.Month, "month");
                y.Map(b => b.Year, "year");
            }).ApplyFilter<MonthsFilter>("year * 12 + month BETWEEN :startMonths and :endMonths");
    }
}

最后，您将需要在发出查询之前启用过滤器，如下所示：

using (var session = sessionFactory.OpenSession())
{
    // Enable filter and pass parameters
    var startMonthsValue = 2000 * 12 + 1;    // january 2000
    var endMonthsValue = 2010 * 12 + 3;  // march 2010
    session.EnableFilter("MonthsFilter")
        .SetParameter("startMonths", startMonthsValue)
        .SetParameter("endMonths", endMonthsValue);

    // Create and execute query (no filter for B needed here)
    var list = session.QueryOver<A>()
        .Fetch(x => x.BList).Eager  // Eager fetch to avoid the N+1 problem due to BList lazy load
        .Where(x => x.Active)
        .TransformUsing(Transformers.DistinctRootEntity)    // List only distinct A entities, to avoid duplicated entries due to eager fetch one-to-many relation
        .List();

    // Do whatever you want with the results
    foreach (var item in list)
    {
        Console.WriteLine("A id: {0} - B children count: {1}", item.Id, item.BList.Count());
    }
}

完整的示例：

using FluentNHibernate.Cfg;
using FluentNHibernate.Cfg.Db;
using FluentNHibernate.Mapping;
using NHibernate;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

namespace NHibernateTests
{
    public class A
    {
        public virtual int Id { get; set; }
        public virtual bool Active { get; set; }
        public virtual IEnumerable<B> BList { get; set; }
    }


    public class B
    {
        public virtual int Month { get; set; }
        public virtual int Year { get; set; }
    }


    internal class AMapping : ClassMap<A>
    {
        public AMapping()
        {
            Table("AObjects");

            Id(x => x.Id, "id");
            Map(x => x.Active, "active");

            HasMany(x => x.BList)
                .Table("BObjects")
                .KeyColumn("foreign_id")
                .Component(y => {
                    y.Map(b => b.Month, "month");
                    y.Map(b => b.Year, "year");
                }).ApplyFilter<MonthsFilter>("year * 12 + month BETWEEN :startMonths and :endMonths");
        }
    }

    public class MonthsFilter : FilterDefinition
    {
        public MonthsFilter()
        {
            WithName("MonthsFilter")
                .AddParameter("startMonths", NHibernateUtil.Int32)
                .AddParameter("endMonths", NHibernateUtil.Int32);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var sessionFactory = CreateNHibernateSessionFactory();
            using (var session = sessionFactory.OpenSession())
            {
                // Enable filter and pass parameters
                var startMonthsValue = 2000 * 12 + 1;    // january 2000
                var endMonthsValue = 2010 * 12 + 3;  // march 2010
                session.EnableFilter("MonthsFilter")
                    .SetParameter("startMonths", startMonthsValue)
                    .SetParameter("endMonths", endMonthsValue);

                // Create and execute query (no filter needed here)
                var list = session.QueryOver<A>()
                    .Fetch(x => x.BList).Eager  // Eager fetch to avoid the N+1 problem due to BList lazy load
                    .Where(x => x.Active)
                    .TransformUsing(Transformers.DistinctRootEntity)    // List only distinct A entities, to avoid duplicated entries due to eager fetch one-to-many relation
                    .List();

                // Do whatever you want with the results
                foreach (var item in list)
                {
                    Console.WriteLine("A id: {0} - B children count: {1}", item.Id, item.BList.Count());
                }
            }

            Console.WriteLine("Press ENTER to continue...");
            Console.ReadLine();
        }

        static ISessionFactory CreateNHibernateSessionFactory()
        {
            FluentConfiguration fc = Fluently.Configure()
                .Database(MsSqlConfiguration.MsSql2012.ConnectionString("Server=.\\SQLEXPRESS;Database=NHibernateTests;Trusted_Connection=True;"))
                .Mappings(m => {
                    m.FluentMappings
                        .AddFromAssembly(Assembly.GetExecutingAssembly());
                });

            var config = fc.BuildConfiguration();

            return config.SetProperty(NHibernate.Cfg.Environment.ReleaseConnections, "on_close")
                       .BuildSessionFactory();
        }
    }
}

有关过滤器的更多信息：

答案 1 :(得分：0)

查询中的主要问题-您无法在function nextNumber() { if (typeof (Storage) !== "undefined") { if (localStorage.clickcount) { localStorage.clickcount = Number(localStorage.clickcount) + 1; } else { localStorage.clickcount = 1; } Increment = localStorage.clickcount; } else { } } elem.setAttributeNS(null, "id", "ID " + Increment)//assigning id 中使用计算：

WhereRestrictionOn

此处仅支持映射的属性。 您仍然可以编写所需的查询，但是似乎您必须使用带下划线的.WhereRestrictionOn(y => y.Year * 12 + y.Month) // the problem is here, exception below 帮助方法。像这样：

ICriteria
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