LINQ加入使用日期不工作

我想基于两个单独的列表创建项目的单个列表，但ListA中的日期属性与ListB中的不同日期属性具有相同的值。我从我的FinalList中获取来自ListB的正确对象，但不是ListA中的对象。LINQ加入使用日期不工作

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 
}

而且我的代码

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()

所以我期待FinalList包含对象Foo1和Foo3，但我只得到Foo3

任何想法我做错了吗？

来源

2015-02-05 empo

您正在使用什么课？什么是安装日期？什么是删除日期？你为什么使用IList（Of Object）'？一些样本输入/输出如何？否则，这是不可能回答的。 – sloth 2015-02-05 15:36:49

是'RemovalDate'类型，可以是什么？ – Plutonix 2015-02-05 15:38:08

@Plutonix请注意，VB.Net使用'Nothing'也可以获得类型的默认值（如C＃的default（））。 – sloth 2015-02-05 16:00:57

我已经纠正代码：

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，做一个简单的Join：

Dim FinalList = (From LA In ListA 
       Join LB In ListB On LA.InstallDate Equals LB.RemovalDate).ToList()

FinalList现在包含一个项目（因为有一个匹配）具有两个属性：

LA（Foo1）和LB（Foo2）

enter image description here

在回答您的评论：

要flaten列表，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

enter image description here

来源

2015-02-05 16:13:24 sloth

我需要FinalList是一个单一的对象列表，以便以后迭代。 – empo 2015-02-06 10:04:18

@empo请参阅我的编辑 – sloth 2015-02-06 10:16:05

LINQ加入使用日期不工作

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