NHibernate 3 - 输入安全的方式来选择不同的值列表

发布于 2024-12-03 08:43:47 字数 1191 浏览 1 评论 0原文

我试图从表中选择一个不同的值列表，同时在另一列上排序。

到目前为止，唯一对我有用的方法是使用魔术字符串和对象数组。有更好的（类型安全）方法吗？

  var projectionList = Projections.ProjectionList();
  projectionList.Add(Projections.Property("FolderName"));
  projectionList.Add(Projections.Property("FolderOrder"));

  var list = Session.QueryOver<T>()
    .Where(d => d.Company.Id == SharePointContextHelper.Current.CurrentCompanyId)
    .OrderBy(t => t.FolderOrder).Asc
    .Select(Projections.Distinct(projectionList))
    .List<object[]>()
    .ToList();

  return list.Select(l => new Folder((string)l[0])).ToList();

顺便说一句，使用 linq 执行此操作是行不通的，您必须选择FolderOrder，否则您将收到 sql 错误（如果指定了 SELECT DISTINCT，则 ORDER BY 项必须出现在选择列表中。 ）

然后这样做会产生一个已知错误：此 SelectClauseVisitor 不支持表达式类型“NhDistinctExpression”。关于使用具有 unique

 var q = Session.Query<T>()
    .Where(d => d.Company.Id == SharePointContextHelper.Current.CurrentCompanyId)
    .OrderBy(d => d.FolderOrder)
    .Select(d => new {d.FolderName, d.FolderOrder})
    .Distinct();
  return q.ToList().Select(f => new Folder(f));

All 的匿名类型似乎需要很多麻烦和复杂性来完成一些 sql 基础知识。 ..

原文

I am trying to select a distinct list of values from a table whilst ordering on another column.

The only thing working for me so far uses magic strings and an object array. Any better (type-safe) way?

  var projectionList = Projections.ProjectionList();
  projectionList.Add(Projections.Property("FolderName"));
  projectionList.Add(Projections.Property("FolderOrder"));

  var list = Session.QueryOver<T>()
    .Where(d => d.Company.Id == SharePointContextHelper.Current.CurrentCompanyId)
    .OrderBy(t => t.FolderOrder).Asc
    .Select(Projections.Distinct(projectionList))
    .List<object[]>()
    .ToList();

  return list.Select(l => new Folder((string)l[0])).ToList();

btw, doing it with linq won't work, you must select FolderOrder otherwise you'll get a sql error (ORDER BY items must appear in the select list if SELECT DISTINCT is specified.
)

and then doing that gives a known error : Expression type 'NhDistinctExpression' is not supported by this SelectClauseVisitor. regarding using anonymous types with distinct

 var q = Session.Query<T>()
    .Where(d => d.Company.Id == SharePointContextHelper.Current.CurrentCompanyId)
    .OrderBy(d => d.FolderOrder)
    .Select(d => new {d.FolderName, d.FolderOrder})
    .Distinct();
  return q.ToList().Select(f => new Folder(f));

All seems a lot of hoops and complexity to do some sql basics....

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不奢求什么 2024-12-10 08:43:47

为了解决类型安全问题，语法是：

  var projectionList = Projections.ProjectionList();
  projectionList.Add(Projections.Property<T>(d => d.FolderName));
  projectionList.Add(Projections.Property<T>(d => d.FolderOrder));

To resolve the type-safety issue, the syntax is:

  var projectionList = Projections.ProjectionList();
  projectionList.Add(Projections.Property<T>(d => d.FolderName));
  projectionList.Add(Projections.Property<T>(d => d.FolderOrder));

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