nhibernate - NHibernate QueryOver 投影 - 将集合投影到 DTO

Question

我正在尝试将实体的集合投影到 DTO 中。简单的属性很容易，但集合有问题：

public class Blog
{
   public string Name {get;set;}
   public IList<Comments> Comments {get;set;}
   //... more properties
}
public class Comments
{
   public Blog Blog {get;set;}
   //... more properties
}
public class MyDTO
{
   public string BlogName {get;set;}
   public IList<Comments> {get;set;}
}

查询有点像：

var dto = _session.QueryOver<Blog>(() => blogAlias)
                            .JoinAlias(x => x.Comments, () => commentsAlias, JoinType.LeftOuterJoin)
                            .Select(
                                Projections.Property(() => blogAlias.Reference).WithAlias(() => myDTO.Reference),
                                // what project here to project blogAlias.Comments into myDTO.Comments))
                            .TransformUsing(Transformers.AliasToBean<MyDTO>()
                            .SingleOrDefault<MyDTO>();

编辑更新

即使没有转换，我似乎也无法运行简单的投影并得到：“索引超出了数组的范围”：

  var dto = _session.QueryOver<Blog>(() => blogAlias)
                                .JoinAlias(x => x.Comments, () => commentsAlias, JoinType.LeftOuterJoin)
                                .Select(
                                    Projections.Property(() => blogAlias.Reference).WithAlias(() => myDTO.Reference),
Projections.Property(() => blogAlias.Comments).WithAlias(() => myDTO.Comments)
                                .List<object>();

Answer 1

我猜这是你应该做的..

将您的 DTO 更新为：

public class MyDTO
{
   public string BlogName {get;set;}
   public IList<Comments> Comments {get;set;}
}

您修改后的查询：

var dto = _session.QueryOver<Blog>(() => blogAlias)
          .JoinAlias(x => x.Comments, () => commentsAlias, JoinType.LeftOuterJoin)
          .Select(Projections.Property(() => blogAlias.Reference).WithAlias(() => myDTO.Reference),
                  Projections.Property(() => blogAlias.Comments).WithAlias(() => myDTO.Comments),
          .TransformUsing(Transformers.AliasToBean<MyDTO>()
          .SingleOrDefault<MyDTO>()

如果那不起作用那么

_session.QueryOver<Blog>(() => blogAlias)
              .JoinAlias(x => x.Comments, () => commentsAlias, JoinType.LeftOuterJoin)
              .Select(Projections.Property(() => blogAlias.Reference),
                      Projections.Property(() => blogAlias.Comments))
              .SingleOrDefault<object[]>()
              .Select(x=>new MyDTO {BlogName=(string)x[0],Comments=x[1].Select(y=>y.ToString()).ToList())};