投影，平整结构

Question

我正试图用这两个类进行投影：

public class SomeClass
{
    public virtual int Id { get; private set; }
    public virtual string Name { get; set; }
    public virtual IList<Language> Languages { get; set; }
}
public class Language
{
     public virtual string Code { get; set; }
}

映射如下：

public class SomeClassMapping : ClassMap<SomeClass>
{
    public SomeClassMapping()
    {
        Id(x => x.Id).GeneratedBy.Identity();
        Map(x => x.Name)
            .Length(255)
            .Not.Nullable();
        HasMany(x => x.Languages)
            .KeyColumn("SomeClassId")
            .Table("SomeClassLanguages")
            .Component(x => x.Map(y => y.Code))
            .Cascade.All();
    }    
}
public class LanguageMapping : ComponentMap<Language>
{
    public LanguageMapping()
    {
         Map(x => x.Code);
    }
}

这是应该保存结果的类：

public class SomeClassListItem
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Languages { get; set; }
}

从概念上讲，我想做的是将语言代码制作成一个逗号分隔的列表，它在代码中表达如下：

var items = (from s in _session.Query<SomeClass>()
         orderby s.Name
         select new SomeClassListItem
        {
            Id = s.Id,
            Name = s.Name,
            Languages = s.Languages.Select(x => x.Code).Aggregate((current, language) => current + (language + ", "))
        }).ToList();

关于如何通过LINQ、HQL、ICriteria或其他方式实现这一点，有什么建议吗？

Answer 1

我认为您的概念代码应该能够做到这一点。你唯一想做的就是急切地获取你的Languages集合，以避免2台服务器往返。

var items = _session.Query<SomeClass>().Fetch(s => s.Languages)
                .OrderBy(s => s.Name)
                .Select(s => new SomeClassListItem
                 {
                      Id = s.Id,
                      Name = s.Name,
                      Languages = s.Languages.Select(x => x.Code).Aggregate((current, language) => current + (language + ", "))
                 }).ToList();