Question

I have Window Application in VB.Net. I have following Classes & Enum.

Public Class Page
    Public Property Name As String
    Public Property PageItems As List(Of PageItem)
End Class


Public Class PageItem
    Public Property ItemName As String
    Public Property mode As Mode
End Class

Public Enum Mode
    Mode1
    Mode2
End Enum

In my application I have a List(Of Page) property. One Page may have multiple PageItemand also PageItem.ItemName can be duplicated with different modes. e.g. Application can have a PageItem with Mode1 and Mode2 (Here it’s possible that Mode1 item may in Page(0) and Mode2 item may in Page(1))

My Question is How to find a PageItems List (Same ItemName) which have both Mode1 and Mode2 from a List(Of Page) property using LINQ ?

Example:

Page 1 has 3 Items {Item1, Mode1}, {Item2,Mode1}, {Item3,Mode2}

Page 2 has 2 Items {Item1, Mode2}, {Item4, Mode1}

Here I want a PageItems list which have both mode Mode1 & Mode2. In the above case the result should be {Item1, Mode1}, {Item1, Mode2} (Item1 have both Modes)

Answer 1

As you need “groups of PageItems”, I went for that approach:

From p In pages From pi In p.PageItems _
 Group By pi.ItemName Into Group _
 Where (New Mode(){Mode.Mode1, Mode.Mode2}).All(Function(m) _
               (From pig In Group Where pig.pi.Mode = m).Any) _
 Select ItemName, PageItems=(From pig In Group Select pig.pi)

Note the final Select is reducing the available information. If you remove it you get the pages of each group too.

To test this I used your data set except that I had Item3 with Mode2 (instead of adding a new Mode3 to the enumeration) and now to test the answer to your question in the comments I changed the Item4 to Item3, so that there are two groups returned for my above answer.

The answer to “only get a List(Of PageItems)” is just a change to the last Select line:

From p In pages From pi In p.PageItems _
 Group By pi.ItemName Into Group _
 Where (New Mode(){Mode.Mode1, Mode.Mode2}).All(Function(m) _
               (From pig In Group Where pig.pi.Mode = m).Any) _
 From pig In Group Select pig.pi