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ArrayList.TrimToSize Method

Sets the capacity to the actual number of elements in the ArrayList.

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

public virtual void TrimToSize()

ExceptionCondition
NotSupportedException

The ArrayList is read-only.

-or-

The ArrayList has a fixed size.

This method can be used to minimize a collection's memory overhead if no new elements will be added to the collection.

To reset a ArrayList to its initial state, call the Clear method before calling TrimToSize. Trimming an empty ArrayList sets the capacity of the ArrayList to the default capacity.

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

The following code example shows how to trim the unused portions of the ArrayList and how to clear the values of the ArrayList.

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

   public static void Main()  {

      // Creates and initializes a new ArrayList.
      ArrayList myAL = new ArrayList();
      myAL.Add( "The" );
      myAL.Add( "quick" );
      myAL.Add( "brown" );
      myAL.Add( "fox" );
      myAL.Add( "jumped" );

      // Displays the count, capacity and values of the ArrayList.
      Console.WriteLine( "Initially," );
      Console.WriteLine( "   Count    : {0}", myAL.Count );
      Console.WriteLine( "   Capacity : {0}", myAL.Capacity );
      Console.Write( "   Values:" );
      PrintValues( myAL );

      // Trim the ArrayList.
      myAL.TrimToSize();

      // Displays the count, capacity and values of the ArrayList.
      Console.WriteLine( "After TrimToSize," );
      Console.WriteLine( "   Count    : {0}", myAL.Count );
      Console.WriteLine( "   Capacity : {0}", myAL.Capacity );
      Console.Write( "   Values:" );
      PrintValues( myAL );

      // Clear the ArrayList.
      myAL.Clear();

      // Displays the count, capacity and values of the ArrayList.
      Console.WriteLine( "After Clear," );
      Console.WriteLine( "   Count    : {0}", myAL.Count );
      Console.WriteLine( "   Capacity : {0}", myAL.Capacity );
      Console.Write( "   Values:" );
      PrintValues( myAL );

      // Trim the ArrayList again.
      myAL.TrimToSize();

      // Displays the count, capacity and values of the ArrayList.
      Console.WriteLine( "After the second TrimToSize," );
      Console.WriteLine( "   Count    : {0}", myAL.Count );
      Console.WriteLine( "   Capacity : {0}", myAL.Capacity );
      Console.Write( "   Values:" );
      PrintValues( myAL );
   }

   public static void PrintValues( IEnumerable myList )  {
      foreach ( Object obj in myList )
         Console.Write( "   {0}", obj );
      Console.WriteLine();
   }

}
/* 
This code produces the following output.

Initially,
   Count    : 5
   Capacity : 16
   Values:    The    quick    brown    fox    jumped
After TrimToSize,
   Count    : 5
   Capacity : 5
   Values:    The    quick    brown    fox    jumped
After Clear,
   Count    : 0
   Capacity : 5
   Values:
After the second TrimToSize,
   Count    : 0
   Capacity : 16
   Values:
*/

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0
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