如何让 NHibernate 映射到元组或类? [英] How can I get NHibernate to map to a Tuple or Class?

问题描述

我有以下方法可以从数据库中获取结果列表.

I have the following method to get a list of results from the database.

public static IList<T> Find<T>(DetachedCriteria crit) where T : class
{
    lock (_locker)
    {
        return crit.GetExecutableCriteria(InstanceSession)
            .List<T>();
    }
}

这通常效果很好.但是，我已经更改了一个调用上述方法的方法.

This generally works well. However, I've changed a method that calls the method above from.

public IList<FooBarResult> FindResults(FooBarTask st)
{
    return DataAccess.Find<FooBarResult>(DetachedCriteria.For<FooBarResult>()
        .Add(Restrictions.Eq("Task", st))).ToList();
}

哪个有效(因为我不想返回整个 FooBarResult，只返回其中的某些列).

Which works, to this (as I don't want to return the whole of FooBarResult, just certain columns on it).

public IList<Tuple<DateTime, Guid>> FindResults(FooBarTask st)
{
    return DataAccess.Find<Tuple<DateTime, Guid>>(DetachedCriteria.For<FooBarResult>()
        .Add(Restrictions.Eq("Task", st))
        .SetProjection(
            Projections.ProjectionList()
                .Add(
                    Projections.Property("FieldOne")
                )
                .Add(
                    Projections.Property("FieldTwo")
                )
        )
    )
    .ToList();
}

我希望顶部的 Find 方法会自动将列表的条目转换为 Tuple，但它只返回 System.Object[].

I was hoping that the Find method at the top would automatically cast the entries of the list to Tuple, but it just returns System.Object[].

有什么办法可以让它返回一个元组列表?

Is there any way I can make it return a list of tuples?

推荐答案

您可以尝试使用 SetResultTransformer，如 这个答案:

You can try using SetResultTransformer as explained in this answer:

var tupleConstructor = typeof(Tuple<DateTime, Guid>).GetConstructors()[0];

然后:

 return DataAccess.Find<Tuple<DateTime, Guid>>(DetachedCriteria.For<FooBarResult>()
    .Add(Restrictions.Eq("Task", st))
    .SetProjection(
        Projections.ProjectionList()
            .Add(
                Projections.Property("FieldOne")
            )
            .Add(
                Projections.Property("FieldTwo")
            )
    ).SetResultTransformer(Transformers.AliasToBeanConstructor(tupleConstructor))
).ToList();

这篇关于如何让 NHibernate 映射到元组或类?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！