ArrayList

Question

Hi. i am a beginner at programing. can someone pleas tell me how to do an arraylist which check if an items has been added more than once?

Alan · Answer

Hi Dino, As luck would have it, Mahesh Chand has just written a free book for C# beginners which can be downloaded here: http://www.c-sharpcorner.com/UploadFile/mahesh/csp08202007084545AM/csp.aspx Other good online resources to check out include the following (the second one's best if you already know a bit of C/C++): http://www.publicjoe.co.uk/csharp/csharp.html http://www.charlespetzold.com/dotnet/

Dino S · Answer

Thx Alan. Do you have any idea where i can find a good C# book to study? any specific C# book? Many thx /Dino

Alan · Answer

Here's a possible approach which still works if the ArrayList contains elements of different types: using System; using System.Collections; class Program { static void Main() { ArrayList al = new ArrayList(); al.Add(123); al.Add("hello"); al.Add(456.78); al.Add("hello"); al.Add(456.78); al.Add(true); al.Add(new MyClass()); al.Add(new MyClass()); // different obect, so not duplicated MyClass mc = new MyClass(); al.Add(mc); al.Add(mc); //same object, so duplicated bool containsDuplicates = false; for (int i = 0; i { if (al.IndexOf(al[i], i + 1) > -1) { Console.WriteLine("{0} is duplicated", al[i]); if (!containsDuplicates) containsDuplicates = true; } } if (!containsDuplicates) Console.WriteLine("There are no duplicated objects"); Console.ReadLine(); } } class MyClass { static int lastId; public readonly int Id; public MyClass() { Id = ++lastId; } public override string ToString() { return "MyClass object #" + Id.ToString(); } }

ArrayList

Answers (3)