Array.Resize<T> Method

July 28, 2014

Changes the number of elements of an array to the specified new size.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

public static void Resize<T>(
	ref T[] array,
	int newSize
)

Type Parameters

T

The type of the elements of the array.

Parameters

array
Type: T [] %
The one-dimensional, zero-based array to resize, or null to create a new array with the specified size.
newSize
Type: System.Int32
The size of the new array.

ExceptionCondition
ArgumentOutOfRangeException

newSize is less than zero.

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.

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 following example shows how resizing affects the array.


using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      // Create and initialize a new string array.
      String[] myArr = {"The", "quick", "brown", "fox", "jumps", 
            "over", "the", "lazy", "dog"};

      // Display the values of the array.
      outputBlock.Text +=
          "The string array initially contains the following values:" + "\n";
      PrintIndexAndValues(outputBlock, myArr);

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

      // Display the values of the array.
      outputBlock.Text += String.Format("After resizing to a larger size, ") + "\n";
      outputBlock.Text += "the string array contains the following values:" + "\n";
      PrintIndexAndValues(outputBlock, myArr);

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

      // Display the values of the array.
      outputBlock.Text += String.Format("After resizing to a smaller size, ") + "\n";
      outputBlock.Text += "the string array contains the following values:" + "\n";
      PrintIndexAndValues(outputBlock, myArr);
   }

   public static void PrintIndexAndValues(System.Windows.Controls.TextBlock outputBlock, String[] myArr)
   {
      for (int i = 0; i < myArr.Length; i++)
      {
         outputBlock.Text += String.Format("   [{0}] : {1}", i, myArr[i]) + "\n";
      }
      outputBlock.Text += "\n";
   }
}

/* 
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

*/


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

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