Vb.net 使用日期的LINQ联接不起作用

我试图基于两个单独的列表创建一个项目列表，但是ListA中的日期属性与ListB中的不同日期属性的值相同。我从FinalList中的ListB中获得正确的对象，但不是ListA中的对象

考虑以下数据

Public Class Foo
    Public Property InstallDate  As Nullable(Of Date)
       'getters/ setters 
    End Property
    Public Property RemovalDate  As Nullable(Of Date)
       'getters/ setters 
    End Property
End Class

Dim Foo1 As New Foo()
Foo1.InstallDate = 01/12/2014
Foo1.RemovalDate = Nothing

Dim Foo2 As New Foo() 
Foo2.InstallDate = 02/12/2014
Foo2.RemovalDate = Nothing

Dim Foo3 As New Foo()
Foo3.InstallDate = 01/01/2001
Foo3.RemovalDate = 01/12/2014

Dim OriginalList As IList(Of Foo) = {
   Foo1,
   Foo2,
   Foo3
}

还有我的密码

    Dim ListA As IList(Of Foo) =
        (From X In OriginalList
        Where X.InstallDate IsNot Nothing And X.RemovalDate Is Nothing
        Select X).ToList()

    Dim ListB As IList(Of Foo) =
        (From X In OriginalList
        Where X.RemovalDate IsNot Nothing
        Select X).ToList()

    Dim FinalList As IList(Of Foo) =
        (From LA In ListA
        Group Join LB In ListB On ListA.InstallDate Equals ListB.RemovalDate Into Group _
        From grp In Group.DefaultIfEmpty()
        Select grp).ToList()

所以我希望FinalList包含对象Foo1和Foo3，但我只得到Foo3

---

知道我做错了什么吗？

我已经更正了您的代码：

Public Class Foo
    Public Property InstallDate  As Nullable(Of Date)
    Public Property RemovalDate  As Nullable(Of Date)
End Class

Dim Foo1 As New Foo()
Foo1.InstallDate = #01/12/2014#
Foo1.RemovalDate = Nothing

Dim Foo2 As New Foo() 
Foo2.InstallDate = #02/12/2014#
Foo2.RemovalDate = Nothing

Dim Foo3 As New Foo()
Foo3.InstallDate = #01/01/2001#
Foo3.RemovalDate = #1/12/2014#

Dim OriginalList As IList(Of Foo) = {
    Foo1,
    Foo2,
    Foo3
}

Dim ListA = (From X In OriginalList
             Where X.InstallDate IsNot Nothing AndAlso X.RemovalDate Is Nothing
             Select X).ToList()

Dim ListB = (From X In OriginalList
             Where X.RemovalDate IsNot Nothing
             Select X).ToList()

因此，要获得Foo1和Foo3，请执行一个简单的连接：

FinalList现在包含单个项，因为有一个匹配项具有两个属性：

LA Foo1和LB Foo2

针对你的评论：

要使列表变平，只需使用：

Dim FinalList = From LA In ListA
                Join LB In ListB On LA.InstallDate Equals LB.RemovalDate
                From item in {LA, LB}
                Select item

---

你在上什么课？安装日期是什么时候？什么是拆除日期？为什么要使用IListOf对象？一些输入/输出示例如何？否则，这是不可能回答的。RemovalDate是一个可以为Nothing的类型吗？@puropoix请注意，VB.Net也不使用Nothing来获取类型的默认值，如C的默认值。@sloth已编辑了Question我需要FinalList是一个单独的对象列表，以便随后进行迭代。

Dim FinalList = From LA In ListA
                Join LB In ListB On LA.InstallDate Equals LB.RemovalDate
                From item in {LA, LB}
                Select item