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copied!<p>Have you considered using LINQ's <a href="http://msdn.microsoft.com/en-us/library/bb360913.aspx" rel="nofollow noreferrer">OfType</a> extension method? It wraps an enumerable and filters the elements so that only the ones of the specified type are returned. You could use it like this:</p> <pre><code>list.AddRange(superList.OfType(Of SubClass)()) </code></pre> <p>or even:</p> <pre><code>list = superList.OfType(Of SubClass)().ToList() </code></pre> <p>Sorry if my syntax is off, it's been a while since I've used VB.NET</p> <hr> <p><strong>Edit:</strong> Example, as promised:</p> <pre><code>namespace Demo.ListFilter { using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Collections; class Program { private class SuperClass { } private class SubClassA : SuperClass { } private class SubClassB : SuperClass { } static void Main(string[] args) { var superList = new List<SuperClass>() { new SuperClass(), new SuperClass(), new SuperClass(), new SuperClass(), new SubClassA(), new SubClassA(), new SubClassA(), new SubClassB(), new SubClassB(), new SubClassB(), new SubClassB() }; var listA = new List<SubClassA>(); var listB = new List<SubClassB>(); SplitList(superList, listA, listB); Console.WriteLine("List A: {0}", listA.Count); Console.WriteLine("List B: {0}", listB.Count); Console.WriteLine("Press any key to exit..."); Console.ReadKey(); } static void SplitList(IList superList, params IList[] subLists) { foreach(var subList in subLists) { var type = subList.GetType().GetGenericArguments()[0]; FilterList(superList, subList, type); } } static void FilterList(IList superList, IList subList, Type type) { var ofTypeMethod = typeof(Enumerable).GetMethod("OfType"); var genericMethod = ofTypeMethod.MakeGenericMethod(type); var enumerable = (IEnumerable)genericMethod.Invoke(null, new[] { superList }); foreach(var item in enumerable) { subList.Add(item); } } } } </code></pre> <hr> <p><strong>Another Edit:</strong> You could also combine the methods like this:</p> <pre><code> static void SplitList(IList superList, params IList[] subLists) { var ofTypeMethod = typeof(Enumerable).GetMethod("OfType"); foreach(var subList in subLists) { var subListType = subList.GetType(); var type = subListType.GetGenericArguments()[0]; var genericOfTypeMethod = ofTypeMethod.MakeGenericMethod(type); var enumerable = genericOfTypeMethod.Invoke(null, new[] { superList }); var addRangeMethod = subListType.GetMethod("AddRange"); addRangeMethod.Invoke(subList, new[] { enumerable }); } } </code></pre> <p><em>Don't forget to add error handling!</em></p>

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