Find maximum value in list by condition LINQ VB.Net

Question

Hi All,

I have a list "ItemList" which has a property "Name" and "Pkeylist" PKeyList is a primary key for the list.

        Dim maxAmount = From item In itemList
                                        Where item.Name = "BOX"
                                        Select item.max(Function(x) x.PKeyList)

I would like to find the highest value for the group with Name "BOX" and get the max value form the PKeyList. How can i get that?

Thanks

Answer 1

Hi,
you can user order by descending and take the first item like in following demo:

Module Module62
  Sub Main()
    Try
      Call (New Demo).Execute()
    Catch ex As Exception
      Console.WriteLine(ex.ToString)
    End Try
    Console.WriteLine("Continue enter key")
    Console.ReadKey()
  End Sub

  Friend Class Demo
    Friend Sub Execute()
      Dim itemList As New List(Of Data)
      itemList.Add(New Data With {.Name = $"BOX", .PKeyList = 1})
      itemList.Add(New Data With {.Name = $"BOX", .PKeyList = 3})
      itemList.Add(New Data With {.Name = $"BOX", .PKeyList = 2})

      Dim maxAmount = (From item In itemList
                       Where item.Name = "BOX"
                       Order By item.PKeyList Descending).First.PKeyList
      Console.WriteLine(maxAmount)
    End Sub
  End Class

  Friend Class Data
    Friend Property Name As String
    Friend Property PKeyList As Integer
  End Class

End Module

Answer 2

Thanks peter for the time and effort for writing the whole answer . You could have written only the line "Order By item.PKeyList Descending).First.PKeyList" . Much appreciated.

Answer 3

Dim maxColumnValue As Object = (From x As Class In list(of Class) Select x.ColumnName Order By ColumnName Descending).First

or

Dim maxColumnValue As Object = (From x As Class In list(of Class) Select x.ColumnName Order By ColumnName ).Last