ArrayList.Insert Method (Int32, Object)
Inserts an element into the ArrayList at the specified index.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- index
-
Type:
System.Int32
The zero-based index at which value should be inserted.
- value
-
Type:
System.Object
The Object to insert. The value can be null.
Implements
IList.Insert(Int32, Object)| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | |
| NotSupportedException |
ArrayList accepts null as a valid value and allows duplicate elements.
If Count already equals Capacity, the capacity of the ArrayList is increased by automatically reallocating the internal array, and the existing elements are copied to the new array before the new element is added.
If index is equal to Count, value is added to the end of ArrayList.
In collections of contiguous elements, such as lists, the elements that follow the insertion point move down to accommodate the new element. If the collection is indexed, the indexes of the elements that are moved are also updated. This behavior does not apply to collections where elements are conceptually grouped into buckets, such as a hash table.
This method is an O(n) operation, where n is Count.
The following code example shows how to insert elements into the ArrayList.
Imports System Imports System.Collections Imports Microsoft.VisualBasic Public Class SamplesArrayList Public Shared Sub Main() ' Creates and initializes a new ArrayList using Insert instead of Add. Dim myAL As New ArrayList() myAL.Insert(0, "The") myAL.Insert(1, "fox") myAL.Insert(2, "jumps") myAL.Insert(3, "over") myAL.Insert(4, "the") myAL.Insert(5, "dog") ' Creates and initializes a new Queue. Dim myQueue As New Queue() myQueue.Enqueue("quick") myQueue.Enqueue("brown") ' Displays the ArrayList and the Queue. Console.WriteLine("The ArrayList initially contains the following:") PrintValues(myAL) Console.WriteLine("The Queue initially contains the following:") PrintValues(myQueue) ' Copies the Queue elements to the ArrayList at index 1. myAL.InsertRange(1, myQueue) ' Displays the ArrayList. Console.WriteLine("After adding the Queue, the ArrayList now contains:") PrintValues(myAL) ' Search for "dog" and add "lazy" before it. myAL.Insert(myAL.IndexOf("dog"), "lazy") ' Displays the ArrayList. Console.WriteLine("After adding ""lazy"", the ArrayList now contains:") PrintValues(myAL) ' Add "!!!" at the end. myAL.Insert(myAL.Count, "!!!") ' Displays the ArrayList. Console.WriteLine("After adding ""!!!"", the ArrayList now contains:") PrintValues(myAL) ' Inserting an element beyond Count throws an exception. Try myAL.Insert(myAL.Count + 1, "anystring") Catch myException As Exception Console.WriteLine("Exception: " + myException.ToString()) End Try End Sub Public Shared Sub PrintValues(myList As IEnumerable) Dim obj As [Object] For Each obj In myList Console.Write(" {0}", obj) Next obj Console.WriteLine() End Sub 'PrintValues End Class ' This code produces the following output. ' ' The ArrayList initially contains the following: ' The fox jumps over the dog ' The Queue initially contains the following: ' quick brown ' After adding the Queue, the ArrayList now contains: ' The quick brown fox jumps over the dog ' After adding "lazy", the ArrayList now contains: ' The quick brown fox jumps over the lazy dog ' After adding "!!!", the ArrayList now contains: ' The quick brown fox jumps over the lazy dog !!! ' Exception: System.ArgumentOutOfRangeException: Insertion index was out of range. Must be non-negative and less than or equal to size. ' Parameter name: index ' at System.Collections.ArrayList.Insert(Int32 index, Object value) ' at SamplesArrayList.Main()
Available since 10
.NET Framework
Available since 1.1