如何用linq選擇列表中的複製項目？

Question

Hy Guys！

我有一個列表可能有複製項目的「ObjDay」。我如何選擇它們？

ObjDay是：

Public class ObjDay 
     _date 
     ... 
    End Class 

我試圖做的：

replicatedItems = From d In ObjDaysList _ 
       Order By d._date _ 
       Group d By d._date Into newGroupOfObjDays = Group _ 
       Where newGroupOfObjDays.Count > 1 _ 
       Select newGroupOfObjDays 

但我發現了這個錯誤：

Can't convert object of type 'WhereSelectEnumerableIterator 2[VB$AnonymousType_0 2[System.DateTime,System.Collections.Generic.IEnumerable 1[ObjDay]], System.Collections.Generic.IEnumerable 1[ObjDay]]' in type 'System.Collections.Generic.List`1[ObjDay]'.

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韓國社交協會的幫助！

Answer 1

您正在選擇組，並嘗試將其分配給List(Of ObjDay)。這是行不通的。你可以這樣做：

'Get groups of duplicate items 
Dim groups = From d In ObjDaysList _ 
      Order By d._date _ 
      Group d By d._date Into newGroupOfObjDays = Group _ 
      Where newGroupOfObjDays.Count > 1 _ 
      Select newGroupOfObjDays 

'Get all items from these groups with SelectMany 
replicatedItems = groups.SelectMany(Function(item) item).ToList