ArrayList.Item Property
Assembly: mscorlib (in mscorlib.dll)
| Exception type | Condition |
|---|---|
| index is less than zero. -or- index is equal to or greater than Count. |
ArrayList accepts a null reference (Nothing in Visual Basic) as a valid value and allows duplicate elements.
This property provides the ability to access a specific element in the collection by using the following syntax: myCollection[index].
The C# language uses the this keyword to define the indexers instead of implementing the Item property. Visual Basic implements Item as a default property, which provides the same indexing functionality.
Retrieving the value of this property is an O(1) operation; setting the property is also an O(1) operation.
The following code example creates an ArrayList and adds several items. The example demonstrates accessing elements with the Item property (the indexer in C#), and changing an element by assigning a new value to the Item property for a specified index. The example also shows that the Item property cannot be used to access or add elements outside the current size of the list.
using System; using System.Collections; public class Example { public static void Main() { // Create an empty ArrayList, and add some elements. ArrayList stringList = new ArrayList(); stringList.Add("a"); stringList.Add("abc"); stringList.Add("abcdef"); stringList.Add("abcdefg"); // The Item property is an indexer, so the property name is // not required. Console.WriteLine("Element {0} is \"{1}\"", 2, stringList[2]); // Assigning a value to the property changes the value of // the indexed element. stringList[2] = "abcd"; Console.WriteLine("Element {0} is \"{1}\"", 2, stringList[2]); // Accessing an element outside the current element count // causes an exception. Console.WriteLine("Number of elements in the list: {0}", stringList.Count); try { Console.WriteLine("Element {0} is \"{1}\"", stringList.Count, stringList[stringList.Count]); } catch(ArgumentOutOfRangeException aoore) { Console.WriteLine("stringList({0}) is out of range.", stringList.Count); } // You cannot use the Item property to add new elements. try { stringList[stringList.Count] = "42"; } catch(ArgumentOutOfRangeException aoore) { Console.WriteLine("stringList({0}) is out of range.", stringList.Count); } Console.WriteLine(); for (int i = 0; i < stringList.Count; i++) { Console.WriteLine("Element {0} is \"{1}\"", i, stringList[i]); } Console.WriteLine(); foreach (object o in stringList) { Console.WriteLine(o); } } } /* This code example produces the following output: Element 2 is "abcdef" Element 2 is "abcd" Number of elements in the list: 4 stringList(4) is out of range. stringList(4) is out of range. Element 0 is "a" Element 1 is "abc" Element 2 is "abcd" Element 3 is "abcdefg" a abc abcd abcdefg */
Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.