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PO.NET Generics - Compare two lists and filter: best practice
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  1. PO.NET Generics - Compare two lists and filter: best practice
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    copied!<p>I have two generic lists of type T. Both lists contain same type, and I'd like to create a third list (or a filtered version of list 2) based on the items in list two that do not exist in List 1, based on the ID of each item.</p> <p>Each list holds a "Package" object, which has an ID property.</p> <p>Right now I mocked up the code using For Each loops, which I know is horrible (the Big O is constant time) so I'd like a more efficent method. </p> <p>this code is in VB per project requirments, but I prefer C# - so either code sample would work for me.</p> <pre><code>Private Sub RemoveStockPackagesFromSelection() Dim p As Package Dim packageList As List(Of Package) = New List(Of Package) Dim stockPackageList As List(Of Package) = New List(Of Package) Dim result As List(Of Package) = New List(Of Package) ' Fill list with User's Packages For i As Integer = 0 To ListBox2.Items.Count - 1 p = New Package p.Id = CInt(ListBox2.Items(i).Value) p.Name = ListBox2.Items(i).Text packageList.Add(p) Next ' Fill list with Stock Packages to compare: Dim ds As DataSet = DAL.GetStandardPackages() For Each dr As DataRow In ds.Tables(0).Rows p = New Package p.Id = CInt(dr.Item("id")) stockPackageList.Add(p) Next ' Do Compare and Filter For Each p1 As Package In packageList For Each p2 As Package In stockPackageList If Not p1.Id = p2.Id Then result.Add(p2) End If Next Next ' Here is our new trimmed list: Response.Write(result.Count) End Sub </code></pre> <p>What is a nice and clean LINQ or Lamda way of doing this filtering? What is the Big O of my method and what would be the Big O of the proposed method (just to satify my curiosity).</p> <p>Thanks</p>
 

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