Array.Resize(T[], Int32) Array.Resize(T[], Int32) Array.Resize(T[], Int32) Array.Resize(T[], Int32) Method

Definition

Changes the number of elements of a one-dimensional array to the specified new size.

public:
generic <typename T>
 static void Resize(cli::array <T> ^ % array, int newSize);
public static void Resize<T> (ref T[] array, int newSize);
static member Resize :  * int -> unit
Public Shared Sub Resize(Of T) (ByRef array As T(), newSize As Integer)
Type Parameters
T

The type of the elements of the array.

Parameters
array
T[]

The one-dimensional, zero-based array to resize, or null to create a new array with the specified size.

newSize
Int32 Int32 Int32 Int32

The size of the new array.

Exceptions

Examples

The following example shows how resizing affects the array.

using namespace System;
static void PrintIndexAndValues(array<String^>^myArr)
{
    for(int i = 0; i < myArr->Length; i++)
    {
       Console::WriteLine(L"   [{0}] : {1}", i, myArr[i]);
    }
    Console::WriteLine();
}

int main()
{
   
    // Create and initialize a new string array.
    array<String^>^myArr = {L"The", L"quick", L"brown", L"fox",
        L"jumps", L"over", L"the", L"lazy", L"dog"};
   
    // Display the values of the array.
    Console::WriteLine( 
        L"The string array initially contains the following values:");
    PrintIndexAndValues(myArr);
   
    // Resize the array to a bigger size (five elements larger).
    Array::Resize(myArr, myArr->Length + 5);
   
    // Display the values of the array.
    Console::WriteLine(L"After resizing to a larger size, ");
    Console::WriteLine(L"the string array contains the following values:");
    PrintIndexAndValues(myArr);
   
    // Resize the array to a smaller size (four elements).
    Array::Resize(myArr, 4);
   
    // Display the values of the array.
    Console::WriteLine(L"After resizing to a smaller size, ");
    Console::WriteLine(L"the string array contains the following values:");
    PrintIndexAndValues(myArr);
    return 1;
}

/* 
This code produces the following output.

The string array initially contains the following values:
   [0] : The
   [1] : quick
   [2] : brown
   [3] : fox
   [4] : jumps
   [5] : over
   [6] : the
   [7] : lazy
   [8] : dog

After resizing to a larger size, 
the string array contains the following values:
   [0] : The
   [1] : quick
   [2] : brown
   [3] : fox
   [4] : jumps
   [5] : over
   [6] : the
   [7] : lazy
   [8] : dog
   [9] :
   [10] :
   [11] :
   [12] :
   [13] :

After resizing to a smaller size, 
the string array contains the following values:
   [0] : The
   [1] : quick
   [2] : brown
   [3] : fox

*/
using System;

public class SamplesArray  
{
    public static void Main()  {
 
        // Create and initialize a new string array.
        String[] myArr = {"The", "quick", "brown", "fox", "jumps", 
            "over", "the", "lazy", "dog"};
 
        // Display the values of the array.
        Console.WriteLine( 
            "The string array initially contains the following values:");
        PrintIndexAndValues(myArr);

        // Resize the array to a bigger size (five elements larger).
        Array.Resize(ref myArr, myArr.Length + 5);

        // Display the values of the array.
        Console.WriteLine("After resizing to a larger size, ");
        Console.WriteLine("the string array contains the following values:");
        PrintIndexAndValues(myArr);

        // Resize the array to a smaller size (four elements).
        Array.Resize(ref myArr, 4);

        // Display the values of the array.
        Console.WriteLine("After resizing to a smaller size, ");
        Console.WriteLine("the string array contains the following values:");
        PrintIndexAndValues(myArr);
    }

    public static void PrintIndexAndValues(String[] myArr)  {
        for(int i = 0; i < myArr.Length; i++)  
        {
            Console.WriteLine("   [{0}] : {1}", i, myArr[i]);
        }
        Console.WriteLine();
    }
}

/* 
This code produces the following output.

The string array initially contains the following values:
   [0] : The
   [1] : quick
   [2] : brown
   [3] : fox
   [4] : jumps
   [5] : over
   [6] : the
   [7] : lazy
   [8] : dog

After resizing to a larger size, 
the string array contains the following values:
   [0] : The
   [1] : quick
   [2] : brown
   [3] : fox
   [4] : jumps
   [5] : over
   [6] : the
   [7] : lazy
   [8] : dog
   [9] :
   [10] :
   [11] :
   [12] :
   [13] :

After resizing to a smaller size, 
the string array contains the following values:
   [0] : The
   [1] : quick
   [2] : brown
   [3] : fox

*/
Imports System

Public Class SamplesArray

    Public Shared Sub Main()

        ' Create and initialize a new string array.
        Dim myArr As String() =  {"The", "quick", "brown", "fox", _
            "jumps", "over", "the", "lazy", "dog"}

        ' Display the values of the array.
        Console.WriteLine( _
            "The string array initially contains the following values:")
        PrintIndexAndValues(myArr)

        ' Resize the array to a bigger size (five elements larger).
        Array.Resize(myArr, myArr.Length + 5)

        ' Display the values of the array.
        Console.WriteLine("After resizing to a larger size, ")
        Console.WriteLine("the string array contains the following values:")
        PrintIndexAndValues(myArr)

        ' Resize the array to a smaller size (four elements).
        Array.Resize(myArr, 4)

        ' Display the values of the array.
        Console.WriteLine("After resizing to a smaller size, ")
        Console.WriteLine("the string array contains the following values:")
        PrintIndexAndValues(myArr)

    End Sub 'Main

    Public Shared Sub PrintIndexAndValues(myArr() As String)
        Dim i As Integer
        For i = 0 To myArr.Length - 1
            Console.WriteLine("   [{0}] : {1}", i, myArr(i))
        Next i
        Console.WriteLine()
    End Sub 'PrintIndexAndValues

End Class 'SamplesArray

'This code produces the following output.
'
'The string array initially contains the following values:
'   [0] : The
'   [1] : quick
'   [2] : brown
'   [3] : fox
'   [4] : jumps
'   [5] : over
'   [6] : the
'   [7] : lazy
'   [8] : dog
'
'After resizing to a larger size, 
'the string array contains the following values:
'   [0] : The
'   [1] : quick
'   [2] : brown
'   [3] : fox
'   [4] : jumps
'   [5] : over
'   [6] : the
'   [7] : lazy
'   [8] : dog
'   [9] :
'   [10] :
'   [11] :
'   [12] :
'   [13] :
'
'After resizing to a smaller size, 
'the string array contains the following values:
'   [0] : The
'   [1] : quick
'   [2] : brown
'   [3] : fox

Remarks

This method allocates a new array with the specified size, copies elements from the old array to the new one, and then replaces the old array with the new one. array must be a one-dimensional array.

If array is null, this method creates a new array with the specified size.

If newSize is greater than the Length of the old array, a new array is allocated and all the elements are copied from the old array to the new one. If newSize is less than the Length of the old array, a new array is allocated and elements are copied from the old array to the new one until the new one is filled; the rest of the elements in the old array are ignored. If newSize is equal to the Length of the old array, this method does nothing.

This method is an O(n) operation, where n is newSize.

The Resize method resizes a one-dimensional array only. The Array class does not include a method for resizing multi-dimensional arrays. To do this, you must either provide your own code or call a special-purpose method in a third-party library. The following code illustrates one possible implementation for a method that resizes an array of n dimensions.

using System;

public class Example
{
   public static void Main()
   {
      int[,] arr = new int[10,2];
      for (int n1 = 0; n1 <= arr.GetUpperBound(0); n1++) {
         arr[n1, 0] = n1;
         arr[n1, 1] = n1 * 2;
      } 

      // Make a 2-D array larger in the first dimension.
      arr = (int[,]) ResizeArray(arr, new int[] { 12, 2} );
      for (int ctr = 0; ctr <= arr.GetUpperBound(0); ctr++) 
         Console.WriteLine("{0}: {1}, {2}", ctr, arr[ctr, 0], arr[ctr, 1]);
      Console.WriteLine();


      // Make a 2-D array smaller in the first dimension.
      arr = (int[,]) ResizeArray(arr, new int[] { 2, 2} );
      for (int ctr = 0; ctr <= arr.GetUpperBound(0); ctr++) 
         Console.WriteLine("{0}: {1}, {2}", ctr, arr[ctr, 0], arr[ctr, 1]);
   }

   private static Array ResizeArray(Array arr, int[] newSizes)
   {
      if (newSizes.Length != arr.Rank)
         throw new ArgumentException("arr must have the same number of dimensions " +
                                     "as there are elements in newSizes", "newSizes"); 

      var temp = Array.CreateInstance(arr.GetType().GetElementType(), newSizes);
      int length = arr.Length <= temp.Length ? arr.Length : temp.Length;
      Array.ConstrainedCopy(arr, 0, temp, 0, length);
      return temp;
   }   
}
// The example displays the following output:
//       0: 0, 0
//       1: 1, 2
//       2: 2, 4
//       3: 3, 6
//       4: 4, 8
//       5: 5, 10
//       6: 6, 12
//       7: 7, 14
//       8: 8, 16
//       9: 9, 18
//       10: 0, 0
//       11: 0, 0
//       
//       0: 0, 0
//       1: 1, 2
Module Example
   Public Sub Main()
      Dim arr(9, 1) As Integer
      For n1 As Integer = 0 To arr.GetUpperBound(0)
         arr(n1, 0) = n1
         arr(n1, 1) = n1 * 2
      Next 

      ' Make a 2-D array larger in the first dimension.
      arr = CType(ResizeArray(arr, { 12, 2} ), Integer(,))
      For ctr = 0 To arr.GetUpperBound(0)
         Console.WriteLine("{0}: {1}, {2}", ctr, arr(ctr, 0), arr(ctr, 1))
      Next
      Console.WriteLine()
      
      ' Make a 2-D array smaller in the first dimension.
      arr = CType(ResizeArray(arr, { 2, 2} ), Integer(,))
      For ctr = 0 To arr.GetUpperBound(0)
         Console.WriteLine("{0}: {1}, {2}", ctr, arr(ctr, 0), arr(ctr, 1))
      Next
   End Sub

   Private Function ResizeArray(arr As Array, newSizes() As Integer) As Array
      If newSizes.Length <> arr.Rank Then
         Throw New ArgumentException("arr must have the same number of dimensions " +
                                     "as there are elements in newSizes", "newSizes") 
      End If 

      Dim temp As Array = Array.CreateInstance(arr.GetType().GetElementType(), newSizes)
      Dim length As Integer = If(arr.Length <= temp.Length, arr.Length, temp.Length )
      Array.ConstrainedCopy(arr, 0, temp, 0, length)
      Return temp
   End Function
End Module
' The example displays the following output:
'       0: 0, 0
'       1: 1, 2
'       2: 2, 4
'       3: 3, 6
'       4: 4, 8
'       5: 5, 10
'       6: 6, 12
'       7: 7, 14
'       8: 8, 16
'       9: 9, 18
'       10: 0, 0
'       11: 0, 0
'       
'       0: 0, 0
'       1: 1, 2

Applies to