Question

我有一个包含许多属性的对象列表。

Dim Duplicates As New List(Of ElementObject)
Dim ListOfDuplicates As New List(Of List(Of ElementObject))

For Each Element As ElementObject In Duplicates
   Dim tmpList As List(Of ElementObject)

   'Im looking for list of elements with the same width and height in Duplicates list
   tmpList = Duplicates.FindAll(Function(x) x.Width = Element.Width And x.Height = Element.Height)
   tmpList = tmpLista.OrderBy(Function(x) x.Id).ToList()

   'Here is what I want: I want to look if tmpLista is already in ListOfDuplicates, but this code does not work
   If ListOfDuplicates.Contains(tmpList) Then
      Continue For
   End If

   ListOfDuplicates.Add(tmpList)
Next

如何实现这一点，检查我的另一个对象列表的列表是否已包含该列表？

Answer 1

您可以使用Equals将列表内容与两个警告进行比较：

列表需要以相同的方式排序
列表中的对象必须是等同的。您可以通过覆盖SequenceEquals或通过实现检查相等性的函数来完成此操作。

我更习惯于在C＃中使用lambda表达式更容易编写，我可以在不创建单独模块的情况下创建扩展类。此类提供哈希码计算和比较，以检查相同值的两个元素列表。它为每个列表计算一组哈希码，对哈希码进行排序，然后使用Public Class ElementListComparer Public Shared Function ListsAreEqual(list1 As IEnumerable(Of Element), list2 As IEnumerable(Of Element)) If list1 Is Nothing OrElse list2 Is Nothing Then Return False If Object.ReferenceEquals(list1, list2) Then Return True return GetSortedHashCodes(list1).sequencequal(GetSortedHashCodes(list2)) End Function Public Shared Function GetSortedHashCodes(elements As IEnumerable(Of Element)) Return elements.Select(Function(el As Element) As Long Return CalculateHashCode(el) End Function).OrderBy(Function(hashcode) Return hashcode End Function) End Function Public Shared Function CalculateHashCode(el As Element) As Long Return (el.Height * 397) ^ el.Width End Function End Class比较哈希码集。

ElementListComparer.ListsAreEqual(list1 as IEnumerable(of Element), list2 as IEnumerable(of Element))

所以你打电话给

rake db:migrate

Answer 2

这就是诀窍：

Dim Contain As Boolean = ListOfDuplicates.Any(Function(x) x.SequenceEqual(tmpList))

检查List <of list <t =“”>＆gt;包含List <t>

2 个答案: