Retrieving objects from ArrayList - cast to type?

Question

I\'m taking a basic course in C# programming, and this is a part of our assignment. Very new to programming so I feel more than a bit lost with this.

The assignment is t

Answer 1

You can access single elements in the ArrayList doing a cast, for example...

string s = myArrayList[100] as string;
myArrayList.Remove("hello");
myArrayList[100] = "ciao"; // you don't need a cast here.

You can also iterate through all elements without a cast...

foreach (string s in myArrayList)
    Console.WriteLine(s);

You can also use CopyTo method to copy all items in a string array...

string[] strings = new string[myArrayList.Count];
myArrayList.CopyTo(strings);

You can create another List<string> with all items in the ArrayList. Since ArrayList implements IEnumerable you can call the List<string> constructor.

List<string> mylist = new List<string>(myArrayList);

But this doesn't makes much sense... why you don't just use List<string> directly? Using directly a List<string> seems more useful to me, and is faster. ArrayList still exists mostly for compatibility purposes since generics were introduced in version 2 of the language.

I just noticed that there may be an error in your code:

    while (line != null)
    {   
        fileContent.Add (line);
        line = reader.ReadLine ();
    }

Should be instead

    for (;;)
    {   
        string line = reader.ReadLine();
        if (line == null)
            break;
        fileContent.Add(line);
    }

Answer 2

You cast each element on its own before using it.

Answer 3

You can use linq to do this easily:

This will cast all items to string and return an IEnumerable<string>. It will fail if any items can't be cast to a string:

items.Cast<string>();

This will cast all items that can be to a string and skip over any that can't:

items.OfType<string>();