ArrayList.Insert(Int32, Object) Method

Definition

Namespace:

System.Collections

Assembly:

System.Runtime.dll

Source:

ArrayList.cs

Inserts an element into the ArrayList at the specified index.

public:
 virtual void Insert(int index, System::Object ^ value);

public virtual void Insert (int index, object? value);

abstract member Insert : int * obj -> unit
override this.Insert : int * obj -> unit

Public Overridable Sub Insert (index As Integer, value As Object)

Parameters

index

Int32

The zero-based index at which value should be inserted.

value

Object

The Object to insert. The value can be null.

Implements

Insert(Int32, Object)

Exceptions

ArgumentOutOfRangeException

index is less than zero.

-or-

index is greater than Count.

NotSupportedException

The ArrayList is read-only.

-or-

The ArrayList has a fixed size.

Examples

The following code example shows how to insert elements into the ArrayList.

using namespace System;
using namespace System::Collections;
void PrintValues( IEnumerable^ myList );
int main()
{
   
   // Creates and initializes a new ArrayList using Insert instead of Add.
   ArrayList^ myAL = gcnew 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.
   Queue^ myQueue = gcnew 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 ( Exception^ myException ) 
   {
      Console::WriteLine( "Exception: {0}", myException );
   }

}

void PrintValues( IEnumerable^ myList )
{
   IEnumerator^ myEnum = myList->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Object^ obj = safe_cast<Object^>(myEnum->Current);
      Console::Write( "   {0}", obj );
   }

   Console::WriteLine();
}

/* 
 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()
 */

using System;
using System.Collections;
public class SamplesArrayList  {

   public static void Main()  {

      // Creates and initializes a new ArrayList using Insert instead of Add.
      ArrayList myAL = 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.
      Queue myQueue = 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 ( Exception myException )  {
         Console.WriteLine("Exception: " + myException.ToString());
      }
   }

   public static void PrintValues( IEnumerable myList )  {
      foreach ( Object obj in myList )
         Console.Write( "   {0}", obj );
      Console.WriteLine();
   }
}
/*
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(int index, Object value)
   at SamplesArrayList.Main()
*/

Imports System.Collections

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

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()

Remarks

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.

See also

• InsertRange(Int32, ICollection)
• Add(Object)
• Remove(Object)