LINQ VB如何检查对象列表中的重复项 [英] LINQ VB how to check for duplicates in a list of objects

问题描述

我有一个对象列表，每个对象都有2个相关属性:"ID"和名称".让我们将列表称为"lstOutcomes". 我需要检查列表中是否存在重复项(表示object1.ID = object2.ID等)，如果至少有一个重复项，则设置一个标志(valid = false等).同样，当对象失败时，向用户发送一条消息，提及对象的名称"也是很好的选择.

I have a list of objects, each with 2 relevant properties: "ID" and "Name". Lets call the list "lstOutcomes". I need to check the list for duplicates (meaning object1.ID = object2.ID, etc.) and set a flag (valid = false, or something) if there is at least one duplicate. Also, it would be nice to send a message to the user mentioning the "Name" of the object, when it fails.

我确定我将需要使用Group By运算符来执行此操作，但是我不习惯在LINQ中执行此操作，并且那里的示例只是对我没有帮助. 这篇文章似乎很接近我的需要，但是不完全是，它在C#中.

I am sure I will need to use the Group By operator to do this, but I am not used to doing that in LINQ, and the examples out there are just not helping me. This article seems to be close to what i need, but not quite and it's in C#.

这是一个开始的刺...

Here is a starting stab at it...

Dim duplist = _
    (From o As objectType In lstOutcomes _
    Group o By o.ID Into g = Group _
    Let dups = g.Where(Function(h) g.Count > 1) _
    Order By dups Descending).ToArray

if duplist.count > 0 then
valid = false
end if

帮助?

推荐答案

项目在后面，我只是这样将其砍死:

The project is behind, I just hacked it together like this:

    ' For each outcome, if it is in the list of valid outcomes more than once, and it is not in the list of 
    ' duplicates, add it to the duplicates list.
    Dim lstDuplicates As New List(Of objectType)
    For Each outcome As objectType In lstOutcomes
        'declare a stable outcome variable
        Dim loutcome As objectType = outcome
        If lstOutcomes.Where(Function(o) o.ID = loutcome.ID).Count > 1 _
        AndAlso Not lstDuplicates.Where(Function(d) d.ID = loutcome.ID).Count > 0 Then
            lstDuplicates.Add(outcome)
        End If
    Next
    If lstDuplicates.Count > 0 Then
        valid = False
        sbErrors.Append("There cannot be multiple outcomes of any kind. The following " & lstDuplicates.Count & _
                        " outcomes are duplicates: ")
        For Each dup As objectType In lstDuplicates
            sbErrors.Append("""" & dup.Name & """" & " ")
        Next
        sbErrors.Append("." & vbNewLine)
    End If

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