How to update an ArrayList?

Question

I have an ArrayList that I enumerate through and want to update a property (Class1 property) within the ArrayList.

arrayList = new ArrayList();
Class1 class1 = new Class1();
...
...
arrayList.Add(class1);
...
...
Class1 temp;
IEnumerator ie = arrayList.GetEnumerator();
while (ie.MoveNext())
{
...
...
...
temp = (Class1)ie.Current;
temp.PropertyA = Convert.ToInt32(objDataReader.GetValue(6));
...
...
...
}

I want arrayList to reflect the value change of PropertyA.

The value is updated in temp, but not in arrayList.

Thanks for your help.

Jason

Vulpes · Answer

Actually it works fine with an ArrayList as well: using System; using System.Collections; class Class1 { public int PropertyA {get; set;} } class Test { static void Main() { var arrayList = new ArrayList(); Class1 class1 = new Class1(); class1.PropertyA = 3; arrayList.Add(class1); Class1 temp; IEnumerator ie = arrayList.GetEnumerator(); while (ie.MoveNext()) { temp = (Class1)ie.Current; temp.PropertyA = Convert.ToInt32(6); } Console.WriteLine(((Class1)arrayList[0]).PropertyA); // 6 not 3 Console.ReadKey(); } }

Vulpes · Answer

Like you Andrew I don't use ArrayList or Hashtable any more. I prefer the generic alternatives as there's no need for any casting or (in the case of value types) boxing.

Andrew Fenster · Answer

Sure enough. I didn't try it but I was guessing that the reference got lost somehow when you cast the item. I haven't used an ArrayList even once since .Net 2.0 came out with generic collection classes.

Andrew Fenster · Answer

If you replaced your ArrayList with a List  I think it would work just fine. Here is your slightly revised code: List myList = new List (); Class1 class1 = new Class1(); ... myList .Add(class1); ... Class1 temp; IEnumerator ie = myList.GetEnumerator(); while (ie.MoveNext()) { ... temp = ie.Current; temp.PropertyA = Convert.ToInt32(objDataReader.GetValue(6)); ... }